Autunno 1999

"There he is...look at him!" he cried out. "Goddamn...that son-of-a-bitch is coming"

Frustration, fog and fire - how a terrorist bomb blast 100 kilometers away led to the greatest disaster in aviation history, taking the lives of 583 innocent people.

Spain's Canary Islands - Ilas Canarias - an archipelago of seven major volcanic outcrops between 57 and 250 nautical miles out into the Atlantic Ocean from the Moroccan coast of northwest Africa, have long been a tourist destination rivalling the balmy resorts of the Mediterranean. Even ancient Greek and Roman seafarers knew them as "the Fortunate Isles".

Situated around latitude 28 degrees north, their warm and sunny climate is the envy of Northern Europeans, and for many years the group's two principal cities of Las Palmas on Grand Canary and Santa Cruz on Tenerife were regular ports of call for ocean liners en route to South America and South Africa.

As air travel gradually replaced sea transport in the postwar years, major airports were developed to serve Las Palmas and Santa Cruz to cope with the islands' booming tourist trade. New hotels, catering particularly for Scandinavians, Dutch and Germans, proliferated throughout the islands, with Las Palmas, as the Canary Islands' capital, becoming the principal international airport for the group. Strenuous efforts were also made to attract American tourists, the islands' seaports becoming the starting point for luxury cruises of the Mediterranean.

Sunday March 27, 1977 should have been no different to any other spring day at Las Palmas Airport, with the usual frequent international flights coming and going from all over Europe and from the other side of the Atlantic.

But at 1.15pm that afternoon, the bustling life of the airport passenger terminal was thrown into panic and confusion when a small bomb planted by a terrorist exploded in a florist's shop on the terminal concourse. Airport authorities had been warned of the blast 15 minutes before, so although the bomb caused a good deal of damage inside the terminal building, it was being evacuated at the time and there were no fatalities. However, eight people were injured, one seriously.

Telephoning the Spanish airport administration afterwards, a spokesman for a militant Canary Islands independence movement, speaking from Algeria in North Africa, claimed responsibility for the explosion and hinted that a second bomb was planted somewhere in the terminal building.

Unable to tell whether or not this further threat would eventuate, the local police had no alternative but to instruct the civil aviation authorities at Las Palmas to close the airport pending a thorough search for the second bomb. Their decision inevitably affected far more than airport personnel and waiting passengers: numerous international flights, inbound to Las Palmas from a variety of departure points, were approaching the Canary Islands at the time, some of them within less than an hour's flying time from Las Palmas.

The difficulty was overcome by diverting all inbound Las Palmas traffic to Los Rodeos, the other Canary Islands international airport, serving Santa Cruz on the island of Tenerife, some 50 nautical miles to the northwest (a destination that most, if not all the international flights would be "carrying as an alternate" for Las Palmas in any case).

The only real problem would be one of logistics - the additional traffic would sorely try Los Rodeos airport's capacity for a few hours. The second airport possessed only a single runway, and even its aircraft parking areas had nowhere near the capacity to handle double its normal daily aircraft movements. Even so, it was the only possible option in the circumstances and it was expected that Las Palmas would not be closed for long.

Among the numerous flights from European ports diverted to Los Rodeos was a charter trip flown by KLM's Boeing 747 PH-BUF Operated by KLM as Flight KL4805 on behalf of the Holland International Travel Group, it had departed Amsterdam's Schiphol Airport that morning at 9.31am local time carrying 234 mostly young passengers escaping the Northern European cold for a holiday in the sunny warmth of the Canaries. They included three babies and 48 children. Most were Dutch, but amongst them were two Australians, four Germans and four Americans.

During the flight, many of the passengers were intrigued to find that their pilot in command was the handsome and esteemed Jacob Veldhuyzen van Zanten, KLM's chief training captain for Boeing 747 aircraft, featured in company advertisements and in the current issue of the company's in-flight magazine placed in the back pockets of all the cabin seats.

Captain van Zanten had been flying since 1947 and had been an airline pilot with KLM since 1951 when, as a 24-year-old, he commenced duty as a first officer on DC-3s. He now had nearly 12,000 hours' experience, more than 1500 hours of this time as captain of Boeing 747s. But these days he spent most of his working hours instructing in KLM's simulators.

After its four hour trip from Amsterdam across Belgium, France and Spain, then southwest out over the Atlantic to Tenerife, PH-BUF touched down on Los Rodeos Airport's 3400 meters Runway 30 at 1340 hours GMT (1.10pm local time).

For once the fabled Canary Islands failed to live up to their reputation for fine weather: those on board the KLM Boeing 747 were greeted with the sight of patchy low cloud, light rain, and areas of fog in the distance. The light wind was from the northwest.

The apron area, together with a portion of the main taxiway paralleling the runway, was already fully occupied by diverted aircraft when the KLM 747 arrived at Los Rodeos. The tower controller therefore directed the Dutch crew to vacate the runway via the last intersecting taxiway, continue towards the holding point for the reciprocal Runway 12, and to park the aircraft on the holding area apron next to a Norwegian Boeing 737. A short time afterwards a Danish Boeing 727 and then a SATA DC-8 also landed at Los Rodeos and were directed to park in the same area.

Meanwhile, Captain van Zanten, not knowing how long the reopening of Las Palmas Airport on Grand Canary was likely to be delayed, but conscious of his need to complete the flight there as soon as possible, had instructed his passengers to remain on board PH-BUF. After about 20 minutes however he relented, and they were transported to the airport terminal by bus.

At 1.45pm local time (a little more than half an hour after PH-BUFs arrival), while the Dutch crew were still on the flightdeck discussing how the delay was likely to affect their stringent company duty time limitations, a Pan American Boeing 747, N736PA, landed and taxied to the same holding area, parking directly behind the KLM Boeing 747. Flying in across the Atlantic from John F Kennedy Airport in New York, it too had been diverted to Tenerife from its original destination of Las Palmas.

The PanAm service, designated Flight PA1736, had originated in Los Angeles, where 364 passengers - most of them retirees over 55 years of age - had boarded Clipper Victor for the first stage of a charter flight to Grand Canary. Here they were to join the Royal Cruise Line's ship Golden Odyssey for a 12 day "Mediterranean Highlights" cruise. Departing Los Angeles late the previous afternoon, they had flown direct to New York, landing at John F Kennedy Airport just under five hours later. The Boeing 747 was refueled, 14 more passengers came aboard, and there was a change of crew.

After an hour and a half on the ground, the flight took off again for Las Palmas.

Approaching the Canary Islands six hours later, the PanAm flight crew were informed by Air Traffic Control that Las Palmas Airport on Grand Canary was temporarily closed and that their aircraft was to be diverted to Los Rodeos Airport on Tenerife.

For the crew, this was unwelcome news. Already they had been on duty for the best part of eight hours and the diversion would inevitably add several more hours to the trip and

there were the passengers themselves to consider. It was now nearly 13 hours since most of them had boarded the aircraft at Los Angeles. As well as this, they had experienced an hour and a half's unexpected delay at Los Angeles Airport before their departure late the previous afternoon. They were very tired and the majority of them were no longer young.

The PanAm flight's Captain Victor Grubbs, a 57 year old veteran American pilot of 21,000 hours' experience, sensing from the Spanish air traffic controller's instructions that Las Palmas was expected to reopen before long, therefore asked if, instead of diverting into Los Rodeos, the PanAm flight could continue to Las Palmas and be cleared to join a holding pattern to await the reopening of the airport. N736PA was carrying more than adequate reserve fuel and holding in this way would give them quicker and easier access to a landing at Las Palmas than having to make a further flight from Los Rodeos, with all that entailed in terms of procedures and clearances.

To the disappointment of the seasoned American flight crew - Grubbs, First Officer Robert Bragg, and Flight Engineer George Warns - ATC refused the request, so there was nothing for it but to join the numerous other airline aircraft waiting on the ground at Los Rodeos.

Unknowingly echoing Captain van Zanten's initial decision of half an hour earlier, after landing and parking on Los Rodeos' Runway 12 holding apron as directed behind the KLM Boeing 747 PH-BUF, Captain Grubbs announced that the passengers should remain on board in anticipation of an early clearance on to Las Palmas. But the main cabin doors were opened, some passengers taking advantage of this to breathe the fresh Canary Islands air and to take photographs of what they could see from the aircraft.

Meanwhile, on the flight deck of PH-BUF, Captain van Zanten was becoming increasingly concerned that he and his crew were running out of time as far as their permitted period of duty was concerned. Until a few years previously, a KLM aircraft captain was authorized to exercise his discretion in extending his crew's duty time to meet unforeseen delays and so complete a flight satisfactorily. But because of a number of instances in which serious crew fatigue had jeopardized safety, this provision had been revoked.

Instead, the Dutch civil aviation authority now insisted that flight crew duty times be rigidly observed, even at the cost of having to delay the completion of a flight. Captains who exceeded the limitations were liable to prosecution.

To add to the difficulty, recent changes to the Dutch aviation legislation had made the calculation of precise duty time limitations a complex matter involving a number of different factors, and KLM had instructed crews that the company should be contacted for a ruling if they were in any doubt. Aware that if the reopening of Las Palmas Airport was delayed too long, he would be compelled to remain overnight at Los Rodeos, with all the burden that would involve in arranging appropriate accommodation at short notice for his passengers and crew, Captain van Zanten decided to contact the KLM operations office in Amsterdam by H/F radio while they were waiting. The captain spoke to the duty operations officer himself, outlined the difficulty in which they were placed, and asked for the precise duty time available to them without any infringement of limitations. KLM Amsterdam's advice when it came back to PH-BUF by radio was something of a relief - the crew had until 1800 hours GMT (6.30pm local time).

Shortly afterwards, Los Rodeos Tower called all waiting aircraft on the ground control frequency to advise that Las Palmas Airport was now open again. Despite a rigorous search, no second bomb could be found, and the police concluded that the warning had been a hoax.

In the Los Rodeos Airport terminal, passengers who had left their various aircraft were called over the PA system to begin boarding again via the airport buses provided. All the passengers from the KLM aircraft did so except a travel guide for the Holland International Travel Group, Miss Robina van Lanschot. Having attended to the needs of her charges on the flight from Amsterdam, she decided to stay overnight at Santa Cruz. Her spur of the moment decision was to save her life.

Meanwhile, out at the holding area apron for Runway 12, Captain van Zanten, his anxiety over flight time limitations now relieved by the advice from his company, decided he would refuel for the return flight to Amsterdam before taking off for Las Palmas. There was time to do so now, whereas at Las Palmas, with the number of aircraft that would be descending on it, there might be delays in obtaining fuel. The Dutch crew accordingly ordered fuel to be brought out to the KLM Boeing 747 in tankers - a decision that was in hindsight to seal the fate of both 747s that day at Tenerife.

A short time later, the three smaller airliners parked by the two Boeing 747s - the Boeing 737, DC-8 and Boeing 727 - started their engines and were cleared to taxi for takeoff, the duty runway still being Runway 30. First maneuvering carefully around the massive KLM and PanAm. aircraft to reach the Runway 12 entrance, they then backtracked on the runway until they had bypassed the center portion of the parallel taxiway that was still congested by parked aircraft. At this point they rejoined the main taxiway to continue to the holding point for Runway 30.

Although the weather was showing signs of further deterioration and light rain was still falling intermittently, surface visibility remained satisfactory at about 10 kilometers.

Now it was the PanAm Boeing 747s turn to depart. Aboard N736PA, Captain Grubbs' announcement to his passengers that Las Palmas was finally open for traffic again was greeted with general applause in the cabin - at last they could look forward to joining their cruise ship and getting their heads down for the night, a prospect that seemed almost too good to be true after the best part of 24 wakeful hours since most of them got out of bed at home in California. For the flight on to Las Palmas, N736PA would have two additional passengers - two company staff members had boarded the flight to take advantage of a free ride over to Grand Canary.

But when First Officer Bragg called the tower to request a clearance to start the engines, the ground controller replied that while there was no delay as far as ATC clearances were concerned, the PanAm Boeing 747 could have problems in departing at the moment because the main taxiway was still congested with other parked aircraft. The only way to the holding point for Runway 30 was the route the other aircraft had followed - via the Runway 12 entrance, then backtracking on the runway itself. But KLM's PH-BUF, which was only now beginning to refuel, blocked that way for its PanAm sister ship.

Captain Grubbs somehow contained his frustration. He hadn't wanted to land at Los Rodeos anyway, and if ATC had allowed them to hold in the air as he'd requested, they could be making their approach to Las Palmas by now. To clarify their situation, First Officer Bragg now called the KLM crew on the ground control frequency. "How long will it take you to refuel?" he asked.

"About 35 minutes," he was told with no hint of an apology.

The PanAm crew's only possible alternative was to taxi around the Dutch Boeing 747 as the other three aircraft had done. But this looked doubtful. Los Rodeos Airport had not been designed to handle aircraft as big as the Boeing 747 and the width of the holding area apron did not leave a great deal to spare. Undaunted, First Officer Bragg and Flight Engineer Warns climbed down to the ground to pace out the amount of clearance available. It was insufficient - there was no way N736PA could gain access to the runway until PH-BUF moved out of their way.

Bragg and Warns returned to the flightdeck to convey the unwelcome news to Captain Grubbs - there was nothing they could do but await the pleasure of the Dutch crew.

While the American crew inwardly fumed at this further frustration, the local weather continued to deteriorate. Patches of fog, visible in the distance when they arrived at Los Rodeos, were now blowing in onto the runway. And the low cloud and light rain persisted. Already the surface visibility, which had been some 10 kilometers, was reducing intermittently to between one and a half and three kilometers.

Finally the refueling of PH-BUF was completed. The tanker vehicles drove away, the doors of the aircraft were closed, and the engines were started. But by the time the Dutch crew called the tower on the ground control frequency of 118.7mhz at 1656 hours GMT (4.26pm local time) for permission to start engines, the patchy fog had moved in across the airport to completely obscure the runway, reducing visibility in some places to as little as 300 meters, though this was fluctuating.

Nevertheless, approval was given and shortly afterwards the KLM aircraft was cleared to taxi to the holding point for Runway 12 and instructed to switch to the aerodrome control frequency of 119.7. Two minutes later at 1658 hours, while standing at the holding point for Runway 12, the KLM aircraft called the Tower on the aerodrome control frequency to request a clearance to enter the runway and backtrack to the beginning of Runway 30 for takeoff.

The communications exchanged in English between the Dutch Boeing 747 and the Spanish tower controller went as follows:

KLM: "We require backtrack on Runway 12 for takeoff on Runway 30."

Tower: "Taxi to the holding position for Runway 30 ... taxi into the runway ... leave the runway third to your left."

KLM: "Roger, Sir. Entering the runway at this time ... and we go off the runway again for the beginning of Runway 30."

Tower: "Correction ... taxi straight ahead ... ah ... for the runway ... make ... ah ... backtrack."

KLM: "Roger, make a backtrack ... KL 4805 is now on the runway."

Tower: "Roger."

KLM (half a minute later): "You want us to turn left at Taxiway 1?"

Tower: "Negative, negative ... taxi straight ahead ... ah ... up to the end of the runway ... make backtrack."

KLM: "OK, Sir."

Meanwhile, the PanAm crew, having also sought a clearance to start engines and to taxi, were about to move their Boeing 747 on to the runway at the holding point for Runway 12. At this stage, the visibility on the airfield had deteriorated in the fog conditions to the extent that the tower controllers could see neither the runway itself nor the two taxiing Boeing 747s. The PanAm crew therefore sought confirmation that they were to enter the runway while the KLM aircraft was still using it. At 1702 hours GMT, First Officer Bragg, after switching to the aerodrome control frequency of 119.7, called the tower controller:

PanAm: "Ah ... we were instructed to contact you and also to taxi down the runway ... is that correct?"

Tower: "Affirmative ... taxi into the runway and ... ah ... leave the runway third ... third to your left."

PanAm: "Third to the left ... OK."

Tower: "Third one to your left."

Evidently the Spanish controller's English pronunciation was not entirely clear to the American crew, for Captain Grubbs remarked to First Officer Bragg: "I think he said first." Bragg replied: "I'll ask him again."

Both Boeing 747s were now communicating with the Tower on the same frequency and, before Bragg contacted the controller again, the American crew heard him call the KLM aircraft:

Tower: "KL 4805 ... how many taxiway ... ah ... did you pass?"

KLM: "I think we just passed Taxiway 4 now.

Tower: "OK ... at the end of the runway make one eighty and report ... ah ... ready for ATC clearance."

Taxiing in the fog some distance behind the KLM aircraft, the American crew were having some difficulty in clarifying the controller's instruction in their minds. Bragg was studying a small diagram of Los Rodeos Airport which he had opened in the flip chart on his knee.

"This first [intersecting taxiway] is a 90 degree turn." he explained to Captain Grubbs.

Grubbs: "Yeah - OK."

Bragg: "Must be the third [the controller meant] ... I'll ask him again."

Grubbs: "We could probably go in, it's ... ah ...

Bragg (emphatically): "You've got to make a 90 degree turn!"

Grubbs: (uncertainly) "Yeah ...

Bragg: "Ninety degree turn to get around ... this one further down here is a 45."

Bragg pressed his microphone button and called the Tower: "Would - you confirm that you want us to turn left at the third intersection?"

Tower: "The third one, Sir ... one two three ... third one."

Flight Engineer Warns interposed light heartedly to the other crew members: "We'll make it yet."

As the PanAm crew began to go through their pre-takeoff checks, the tower controller further instructed them to report leaving the runway, and Bragg acknowledged the call. But they were still having difficulty sorting out which taxiway the controller wanted them to use.

"Haven't seen any yet," Grubbs remarked to Bragg as they continued rolling down the runway. "I haven't either," Bragg replied. Then, five seconds later, he exclaimed, "There's one!"

"That's the 90 degree," said Grubbs, as they continued past it. Their pre-takeoff checks were almost complete when they heard the KLM Boeing ask the tower controller if the runway centerline lights could be switched on - the KLM crew needed to know if they were available to assess if visibility met their minimum takeoff conditions.

The controller, having checked, replied that the runway centerline lights were out of service. He also passed this information to the PanAm crew. Even so, both crews were evidently satisfied that runway visibility was sufficient for takeoff.

The PanAm crew then sighted the second taxiway through the fog. "That's two!" the captain exclaimed.

Warns: "Yeah ... that's the 45 [degrees] there."

Bragg: "That's this one right here."

Grubbs: "Yeah ... I know "

Warns: "Next one is almost a 45..."

Grubbs: "But it does ... it goes ... ahead. I think it's gonna put us on the taxiway."

"Maybe he counts these as three," Bragg said as the PanAm Boeing 747 continued rolling down the runway past the connecting taxiway intersection.

Aboard the KLM Boeing, which had now reached the end of the runway, Captain van Zanten was at this moment maneuvering his huge aircraft round through 180 degrees to face the direction of takeoff. Just after 1705 hours, as First Officer Klass Meurs finished the pre-takeoff check list, van Zanten opened the throttles slightly and the aircraft began to inch forward. Meurs checked him: "Wait a minute we don't have an ATC clearance.

Van Zanten held the aircraft on the brakes: "No ... I know that. Go ahead and ask."

Meurs called the Tower as the controller instructed: "KL 4805 is now ready for takeoff ... we're waiting for our ATC clearance."

Tower: "KL 4805 ... you are cleared to the Papa beacon ... climb to and maintain Flight Level 90 ... right turn after takeoff ... proceed with heading 040 until intercepting the 325 radial from Las Palmas VOR."

As Meurs began to read back the clearance to the tower controller, van Zanten released the KLM Boeing's brakes and began advancing the throttles to takeoff power. "Let's go," he called to Flight Engineer Willem Schreuder, "Check thrust."

First Officer Meurs, still transmitting to the Tower, continued: "Roger, sir, we are cleared to the Papa beacon, Flight Level 90 until intercepting the 325." By this time the KLM aircraft was six seconds into its takeoff run, so he added: "We are now at takeoff."

Tower: (Interpreting the KLM transmission to mean that the Boeing 747 was ready for takeoff): "OK ... standby for takeoff ... I will call you."

Hearing the beginning of this exchange between the KLM aircraft and the Tower, the PanAm crew were understandably alarmed: "We are still taxiing down the runway!" Bragg transmitted urgently.

Tower: "Roger, PanAm, 1736, report the runway clear."

PanAm: "OK ... will report when we are clear."

Tower: "Thank you"

Fatefully, PanAm's protesting transmission conflicted with the controller's instruction to KLM. Instead of the words "standby for takeoff ... I will call you," all the KLM crew heard after the controller's first "OK" was a squeal resulting from the two simultaneous transmissions on the same frequency.

The exchange that followed between the Tower and the PanAm 747 was however audible on the KLM flightdeck. But by this time the KLM Boeing was 20 seconds into its takeoff run. With Captain van Zanten and First Officer Meurs both concentrating fully on the takeoff itself, only Flight Engineer Schreuder took in the possible significance of the two transmissions. "Did he not clear the runway then?" he asked the pilots.

The captain, giving all his attention to the takeoff, did not take in the engineer's question either. "What did you say?" he asked over his shoulder.

"Did he not clear the runway - that Pan American?" Schreuder repeated.

"Yes, he did," both pilots answered emphatically.

The KLM takeoff continued.

At this stage, the PanAm Boeing, its crew having missed the intersection for Taxiway 3 which the Tower had directed them to take, and unaware of what the other 747 was doing, was still on the runway, approaching Taxiway 4.

Captain Grubbs, still uneasy about occupying the runway in such poor visibility with the KLM aircraft's takeoff obviously imminent, was keen to be out of its way as soon as possible.

"Let's get the hell right out of here," he remarked to his crew:

"Yeah ... he's anxious, isn't he?" Bragg agreed.

"After he's held us up for all this time," enjoined Warns, "Now he's in a rush."

A few seconds later, the PanAm crew caught sight of lights that were materializing through the fog directly ahead. Hazy at first, they seemed for a long moment to be stationary. But as they continued to brighten, it quickly became obvious they were approaching fast!

Grubbs stared through the windscreen in stunned disbelief. "There he is ... look at him!" he cried out. "Goddamn ... that son-of-a-bitch is coming!" Desperately pushing all four throttles wide open, he attempted to swing the Boeing 747 off the runway to the left.

"Get off! Get off! Get off!" Bragg yelled frantically as he saw the other aircraft's nose begin to rise into the takeoff attitude.

Aboard the hurtling Dutch aircraft, First Officer Meurs' eyes were fixed on his steadily rising airspeed indicator. "V1" he finally called.

At the same moment, van Zanten sighted the PanAm 747 slewing, across the runway ahead of them. Instinctively - there was no hope of stopping - he hauled back on the control column to try and lift over the American. But too suddenly the tail bumper struck the runway, emitting a shower of metallic sparks.

But lift the KLM aircraft did - just before reaching the other - only it was too late. Its nose leg cleared the PanAm fuselage, but at 140 knots the main undercarriage slammed into it, slicing off the fuselage top as the No 4 engine demolished the hump just behind the flight deck, and both aircraft exploded into flames.

For a few seconds more the burning Dutch aircraft remained in the air, then fell back on to the runway, slewing through 90 degrees before coming to rest with its engines torn off, 150 meters further along the runway. None of the fuselage doors were opened before its fuel tanks exploded, enveloping the entire aircraft in a raging fire.

Aboard the PanAm aircraft, the nightmare of impacts, flash fires, smoke and explosions created utter terror and confusion. Momentarily, First Officer Bragg grabbed for the engine fire shutoff handles above his head. They were not there - the entire top of the fuselage had been carried away!

Moments later the flight deck floor, together with that of the wrecked upper deck, collapsed, spilling the uninjured flight crew and the traumatized bodies of passengers who had been seated in the upper deck lounge into the main deck First Class cabin below. Together with passengers from this section of the aircraft, the crew escaped down on to the ground through a hole torn in the port side of the fuselage.

For once, those in the nose of the aircraft proved to be the lucky ones. Many of those seated on the starboard side of the main cabin in the areas of the initial impact were killed outright. On the port side, and further back in the main cabin, many other passengers who were initially spared injury were trapped and prevented from escaping by collapsed sections of the starboard fuselage side. They were soon overcome by the rapidly spreading fire.

Despite a fire under the port wing, where the engines were still running down, many managed to escape through the port side over-wing exits on to the wing. But they then had to jump to the ground, some sustaining broken legs or other injuries. Still others jumped 20 feet to the ground from a rear door. Within one minute, the evacuation of survivors was effectively over. Fire had now overwhelmed the fuselage and starboard wing of the PanAm Boeing, and those who had not already made their escape would never do so.

Because of the fog, the tower controllers did not see the collision of the two huge aircraft. They heard only the series of explosions, unable to localize them or know their cause. Moments later, the crew of one of the aircraft on the parking apron reported seeing a fire through the fog, but again was unable to specify its exact location or cause.

Immediately the tower controllers sounded the fire alarm, instructing the fire service to be ready for an urgent departure as soon as the position of the fire was known. Shortly afterwards an airport workman came running to the fire station to say there was a fire "to the left of the aircraft parking area."

Vague though this was, it was the first indication of the fire's location. Fire fighting vehicles left at once, but had to pick their way carefully through the congested apron to avoid colliding with parked aircraft. Finally they were able to make out a bright light through the fog, and as they approached, were able to feel the heat. Then they saw the fire itself - it was a big aircraft totally enveloped in fierce flame, the only part visible being the fin and rudder.

As the fire service began fighting the fire, the fog cleared slightly and they sighted another bright light further away. Taking it to be a separated section of the burning aircraft, some fire vehicles went on to this fire, only to discover it was a second large aircraft burning fiercely. All the fire vehicles then moved to concentrate on this second aircraft because the first was obviously now utterly beyond saving.

As a result of this decision, the fire service were there in time to prevent the port wing of the PanAm Boeing from being consumed by the flames (between 15 and 20 tons of fuel were subsequently recovered from it). It was not until the early hours of the following morning that the KLM aircraft fire was totally extinguished.

Because of the dense fog, the tower controllers remained unaware of the exact location of the fire for some minutes, and whether one or two aircraft were involved. But there were five ambulances at the airport at the time and these, following the fire fighting vehicles, were soon on the scene. A standing airport emergency plan designed to cope with a major disaster was quickly implemented, with further medical and ambulance assistance coming from the city of Santa Cruz, and all the injured survivors were soon on their way to hospitals in the city.

When a tally could finally be taken of the cost of the horrific disaster in terms of casualties, it was found that all 234 passengers and 14 crew members aboard KLM's PH-BUF had perished in the intense fire. Another 326 aboard PanAm's N736PA died in the actual crash, including nine members of the cabin crew. Amazingly, there were 70 survivors from the PanAm aircraft, but nine of these later succumbed to their injuries and severe burns, bringing the total number of deaths to 583. The PanAm flight crew all survived, together with the two company staff who had boarded the aircraft at Tenerife and were occupying jump seats on the flight deck, this nose section of the aircraft having just missed being struck by the KLM Boeing's No 4 engine.

Because of the magnitude of the disaster, it was agreed by the Spanish Justice Department that pathologists from Holland and the US should work as a team with Spanish medical authorities in the enormous task of body identifications and, where possible, autopsies. The state of the bodies made it impossible to perform autopsies on the remains of the KLM flight crew.

Not far from the site of the collision, in one of Los Rodeos Airport's cavernous hangars, mute evidence of the worst disaster in aviation history gradually accumulated. As emergency and medical workers completed their tasks, row after row of dark wooden coffins progressively filled the entire floor of the makeshift morgue in the 2500 square meters building - by far the greatest number of fatalities that had ever resulted from one aviation accident.

No less than 70 air safety investigators - from Spain, The Netherlands, the USA, and from the two airline companies involved - descended upon Los Rodeos Airport to probe the cause of this most disastrous of all air accidents.

They found the airport to be located on a plateau, 2000 feet above sea level, with hills lying on either side, a factor that gives rise to somewhat unpredictable weather and frequent low cloud in the vicinity of the airport.

Los Redoes' single runway, aligned southeast - northwest (Runways 12 and 30), was 3400 meters long and 45 meters wide, with 60 meters overruns at both ends. The terminal area lies on the northeastern side of the runway, with a main taxiway parallel to the runway connecting the main apron to holding points at both ends of the runway (see diagram). Adjacent to both runway holding points were smaller apron areas capable of accommodating several airline aircraft at once. In between the runway holding areas, four separate short taxiways linked the main taxiway with the runway.

Three questions were uppermost in the investigators' minds as they began their formidable task:

• Why had Captain Jacob van Zanten, a senior, highly experienced training captain, who had been with the respected KLM, an airline renowned for its safety record, for 25 years, commenced takeoff on Runway 30 without the control tower's clearance to do so?
• Why had Captain Victor Grubbs been instructed by the tower controller to vacate the runway at Taxiway 3, one that led back towards the main apron at an angle of 135 degrees from the runway, rather than the far more conveniently placed 45 degree angled Taxiway 4, leading towards the holding point for Runway 30? And unexpected as this instruction was, why had Captain Grubbs disregarded it? If he had made the earlier turn, the PanAm aircraft would probably have been clear of the runway by the time the KLM Boeing reached that point on its takeoff run.
• Why did the KLM crew not grasp the significance of the PanAm aircraft's report that it had not yet cleared the runway, and would report again to the Tower when it did?

Beginning their inquiry at the crash site itself, the investigators found that the distance of the KLM wreckage from the commencement of Runway 30 was around 1835 meters. The PanAm wreckage lay 450 meters closer to the runway threshold, the KLM aircraft having continued in Right for about 150 meters after striking the upper fuselage of N736PA, before falling back on to the runway and sliding a further 300 meters. Both aircraft were completely destroyed, only the outer two thirds of the port wing of N736PA surviving the fire.

At the moment of impact, the PanAm aircraft was slewed across the runway at an angle of about 45 degrees, as its crew desperately tried to maneuver out of the path of the oncoming KLM Boeing. The latter was fully airborne, its tail bumper having scraped the runway as a result of over-rotation for a distance of 20 meters before it finally lifted off only 80 meters short of N736PA.

But it was too late. Although PH-BUF's nose undercarriage cleared N736PA’s fuselage, its main undercarriage did not, impacting initially against the PanAm aircraft's No 3 engine and fuselage. One of the KLM's undercarriage bogies was wrenched off, but the rest of the main undercarriage and the underside of PH-BUF's rear fuselage rode across the cabin top of N736PA, shearing it off. As both aircraft exploded into flames, the port wing of PH-BUF sliced off N763PA’s tail fin.

As there was no evidence of any failure in either aircraft prior to the impact, and there was every reason to suspect that the accident had resulted from misunderstandings or a lack of adequate communication, the key to the cause of the disaster would most probably be found in the transcriptions of the two Boeing 747's Cockpit Voice Recorders and the continuous tape recording of the Los Rodeos air traffic controllers' communications.

Fortunately the CVRs of both aircraft were recovered from the wreckage and both proved capable of being read out satisfactorily. These readouts were correlated with that of the control tower recording to produce a complete, accurately timed record of all that took place on the flight decks of both Boeing 747s and in the Los Rodeos Control Tower, from before the time the two aircraft started their engines, up to the instant of impact.

It was evident from a careful analysis of all the recorded exchanges that Captain van Zanten, as soon as he heard the ATC clearance being passed to his crew, believed that PH-BUF had been cleared for takeoff and immediately opened the throttles to do so.

But the clearance given them was an airways clearance, applicable only after the aircraft was airborne from Los Rodeos Airport, and not clearance to takeoff.

Thus the fundamental factors in the development of the accident were that PH-BUF:

• Took off without being cleared to do so.
• Did not heed the tower controller's instruction to "standby for takeoff".
• Did not abandon the takeoff when it became apparent that N736PA might still be on the runway.

But how could a senior airline pilot with the technical capacity and experience of Captain van Zanten, whose demeanor during his time on the ground at Los Rodeos seemed perfectly normal, commit such a basic error only a few minutes afterwards - despite several warnings addressed to him?

There were a number of factors that could have contributed to his situation:

• An increasing feeling of tension as the imperative to depart increased. Though reassured by the information radioed from KLM Amsterdam about the duty time still available to him and his crew, they were nevertheless committed to leaving Los Rodeos within a relatively short time, if the flight was not to remain there overnight - with all the resulting inconvenience to the passengers and expense to the company.
• The weather conditions at the airport had suddenly deteriorated and the runway visibility was already uncomfortably close to the minimum specified by KLM for takeoff. For Captain van Zanten it would have seemed important to get airborne quickly, especially as the runway centerline lighting was out of service. Otherwise they might have to wait for an improvement in the weather, with the risk of exceeding the crew's duty time limit. This anxiety to depart was apparent even to the PanAm crew, as was evident from the latter's flight deck conversation while they themselves were taxiing for takeoff.
• Although Captain van Zanten had flown for many years on KLM's European and intercontinental routes, he had been an instructor for 10 years, spending much of his duty time during those years in the company's simulators at Schiphol Airport in Amsterdam. This tended to reduce his day to day familiarity with route flying and its procedures. At the same time his experience and high standing in the company probably made his crew reluctant to question his decisions. In addition, his first officer was a former DC-8 captain who had only recently qualified to crew Boeing 747 aircraft and whose experience on the type was limited to only 95 hours. Having now found himself flying with the training captain who had given him his Boeing 747 rating, he would have been even more circumspect in his attitude to Captain van Zanten.
• While the KLM crew were taxiing for takeoff, the tower controller offered them their ATC [airways] clearance. They declined to accept it at the time, presumably because they were engrossed in performing their pre takeoff checks and it would have distracted them from this vital task. But this meant that when they had finally lined up on the runway and were in all other respects ready for takeoff, they still had to obtain both their airways and takeoff clearances. This fact was perhaps obscured by First Officer Meurs when, after Captain van Zanten began to let the aircraft roll forward on completion of the pre takeoff checks, he told the captain: "Wait ... we don't have an ATC [airways] clearance".

First Officer Meurs' subsequent transmission to the Tower, "KL 4805 is now ready for takeoff and we are waiting for our ATC clearance," though ambiguous, was in effect a simultaneous request for both clearances. That is evidently how Captain van Zanten interpreted it, for when the Tower transmitted the airways clearance only, he immediately accepted it as the takeoff clearance, released the brakes and opened the throttles. Meurs, if he in fact realized the captain's error at this stage, did nothing more to bring it to his attention.

For Captain van Zanten, the misunderstanding resulted in his believing they were cleared both for takeoff and for the airway route. For the controller on the other hand, it resulted in the conviction that PH-BUF was still awaiting its takeoff clearance at the runway threshold.

The further transmission by First Officer Meurs on completing the mandatory readback of the airways clearance when the aircraft was already six seconds into its takeoff run, "We are now at takeoff", was then interpreted by the controller as confirming that the aircraft was at the "takeoff position" on the runway, awaiting its clearance to begin rolling.

Because it was probably the last possible opportunity to avert the unfolding disaster, it was nothing less than tragic that the PanAm crew's understandably alarmed response to these transmissions, "We are still taxiing down the runway!", coincided with the controller's further transmission: "OK ... standby for takeoff ... I will call you." The result was that the KLM crew heard only the controller's "OK", followed by a squeal resulting from the simultaneous transmissions.

The brief exchange that followed between the Tower and the PanAm crew, concerning reporting when the runway was clear, apparently fell on deaf ears as far as the two KLM pilots were concerned, concentrating as they were on their takeoff. But Flight Engineer Schreuder was sufficiently concerned to query the captain about it. What prompted both pilots to give him such an emphatic assurance that the runway was already clear, can never be known. However, the KLM crew's overall failure to monitor the radio communications between the Tower and the PanAm Boeing while both aircraft were taxiing resulted in their having no mental "picture" of its whereabouts on the airfield - a "picture" that could have prevented the accident.

It could also be said that a contributing factor to the accident was the fact that the PanAm crew, while taxiing on the runway in the severely limited visibility, bypassed Taxiway 3 where they had been instructed to turn off and were only 150 meters from Taxiway 4. As a result of a careful analysis of the PanAm aircraft's movements, the investigators found that if it had in fact turned off at Taxiway 3, in all probability no collision would have occurred.

The PanAm crew obviously had difficulty interpreting the tower controller's instruction. In the first place, because of language difficulties, they were unsure whether the controller had nominated Taxiway 1 or Taxiway 3 and, after a further exchange clarified this, they experienced problems in identifying the actual taxiways in the reduced visibility. Their efforts were probably not helped by the pre takeoff checks they were conducting at the same time, and First Officer Bragg had only a small diagram of the airport.

But none of the taxiway intersections on the airport were indicated by markers, and the fact that the third taxiway they saw appeared to lead back towards the congested airport apron at an angle of 135 degrees from the direction in which they were heading, convinced them it was inactive and could not be the taxiway the controller meant.

Apart from the congestion on the apron which they were backtracking on the runway to avoid, it seemed to the PanAm crew that the controller would not ask an aircraft as big as a Boeing 747 to make such a tight turn on to a comparatively narrow taxiway, requiring a similarly tight 135 degree turn in the opposite direction to regain the main taxiway leading to the runway.

Their belief was further reinforced when they saw from the airport diagram that the next taxiway led off the runway at a comfortable 45 degree angle to connect with the main taxiway leading to the holding point for Runway 30. Though they had been careful to query the Tower's initial instruction to backtrack on the runway in the poor visibility before presuming to enter the runway, they did not do so on this occasion, but continued towards Taxiway 4, believing it to be the one nominated.

A final consideration in the fateful sequence of events leading to the disaster was the actions and decisions of the tower controllers themselves. In the first place, the air-field controller's command of English left something to be desired, resulting in misunderstandings on the part of both the American and the Dutch crews. Secondly, the controller, as with the KLM first officer, did not adhere to standard terminology in his communications, giving further opportunity for misunderstanding and misinterpretation.

The tower controller's decision to allow two aircraft to use the runway at the same time was undoubtedly a dangerous one in weather conditions which prevented the controller and the two aircraft concerned from seeing one another.

In the circumstances that had overtaken Los Rodeos Airport, there was little choice but to do so, but the lack of visibility could have been offset by having the aircraft read back all the Tower's instructions and subsequently confirm their various movements and positions.

As it was, with none of the parties in visual contact, the tower controller and the two aircraft were depending entirely on radio communication for knowledge of position. Only by careful read backs, and confirmation of instructions therefore, could safety have been assured.

Against all this, it has to be said that the controller had been on duty all day, during which he had been under pressure handling an unusually high workload because of the number of aircraft diverted to Los Rodeos. He also had relatively little experience in handling Boeing 747 aircraft. His instruction to the PanAm crew to vacate the runway at Taxiway 3 was thus a consequence of his limited appreciation of the maneuverability of the aircraft type. He had not asked the impossible however, as taxiing tests with a Boeing 747 during the investigation subsequently established.

Overall, the investigation determined that, even apart from the shortcomings that existed in the radio communications and the misunderstandings that arose from them, the accident was the final outcome of an unfavorable coincidence of a whole chain of circumstances that individually were relatively insignificant. If any one of these circumstances had not been in place, the accident would not have happened.

It was the seemingly predestined way in which these largely everyday circumstances happened to coincide at Los Rodeos on Sunday, March 27, 1977, that developed the accident to its terrible inevitability.

Above all however, the accident was an appallingly tragic lesson on the danger of depending on radio communication alone for the safe operation and regulation of air traffic. The facts of the accident show that information transmitted by radio communication can be understood in a different way to that intended, as a result of ambiguous terminology and/or the obliteration of key words or phrases. They demonstrate beyond doubt that the oral transmission of essential information, via single and vulnerable radio contacts, carries with it great potential dangers.

The primary safety message drawn from the accident was the urgent need to improve communication between aircraft and Tower. Such communications lagged far behind the fail-safe principle applied to other aspects of aviation. Radio communication, as it existed at Los Rodeos Airport on the day of the accident, was not fail-safe.

Operational measures recommended for immediate adoption as a short term improvement included:

• The use of concise and unambiguous terminology.
• Avoiding the expression "takeoff' in airways clearances.
• Allowing a distinct time interval between the transmission of an airways clearance and a takeoff clearance.

These recommendations were referred to the Air Navigation Commission of the International Civil Aviation Organization (ICAO) for study.

Longer term improvements for the introduction of fail-safe principles in communication between aircraft and Tower were also considered. In its most simple form, this could be no more than a red-green light at the threshold of the runway to confirm the controller's oral takeoff clearance. The FAA in the USA had been testing this system at Atlantic City Airport with encouraging results.

For all who lost loved ones, or were injured, or who were involved in other ways in the horror at Los Rodeos Airport that fateful Sunday afternoon on the island of Tenerife, there would have been a seemingly endless sense of recrimination as they thought over what had happened. There were so many "ifs" - so many small coincidences that need not have compounded to make the tragedy inevitable.

If the bomb had not gone off at Las Palmas, if the PanAm Boeing had been permitted to hold instead of landing at Los Rodeos, if the KLM crew had not decided to refuel, if the PanAm aircraft could have squeezed past its KLM sister ship without having to wait for it to move, if the weather had not deteriorated, if the PanAm crew had not bypassed the No 3 taxiway, if they had not transmitted at the moment they did when they feared the KLM aircraft was about to takeoff, if the KLM captain had taken more notice of his flight engineer's doubt ... any of these factors could have altered the whole course of events as they unfolded.

But no amount of speculation could now change even one of them, much less bring back those who were lost.

The best that could be hoped for was that 583 people had not died in vain - that the sheer magnitude of the disaster would forcibly sheet home to all involved in aviation that, by its very nature, flying abounds with countless opportunities for "little" things to go wrong.

That, to be routinely safe, aviation requires constant and unswerving vigilance on the part of all its professionals - and that those who carry such responsibilities can never afford to take anything for granted.