With visibility deteriorating by the minute, the KLM pilot attempted to leave first. After maneuvering onto the runway, KLM Captain Jacob Veldhuyzen van Zanten -- one of Holland's most experienced aviators -- put the jet into position to take off and ordered his crew to obtain tower clearance.
But for whatever reason, van Zanten did not wait for the clearance before he opened the throttles and began his takeoff roll. Although van Zanten asked for tower clearance, audio tapes taken from the cockpit and control tower clearly showed that it was never issued.
However, one member of the Dutch crew did raise concern that perhaps they were not in the clear. Upon hearing over the radio that both the tower and the Pan Am crew were indicating the jet was not clear of the runway, KLM flight engineer Willem Schreuder can be heard on the cockpit tapes asking Captain van Zanten, "Is he not clear, that Pan American?" To which the captain replied, "oh, yes," and continued his takeoff roll.
With 235 passengers and 14 crewmembers on board, almost zero visibility -- and the Pan Am still on the runway ahead -- the KLM 747 thundered down the air strip.THE PAN AM:
While the KLM crew seemed to be somewhat confused about the situation, the crew aboard the Pan Am jet was well aware of the unfolding situation: They were still on the runway, and the KLM pilot had seemed to indicate that he wasn't waiting for them to get off.
According to the Pan Am's voice recorder, someone in the cockpit -- aware that the KLM was on its way -- grabbed the radio and frantically shouted, "we're still taxiing down the runway!" However, this transmission was unheard because of a technological limitation in the airport's communications system.
In 1977, airport radio systems permitted just one person to speak at a time. When more than one person tried to speak at the same time, a mild whistling sound, known as a heterodyne, is heard over the system instead. At the time the Pan Am radioed their urgent message, someone else was trying to speak, and a heterodyne was created.
A few moments later, Pan Am Captain Victor Grubbs exclaimed, "There he is!," upon seeing the lights of the KLM coming toward him. When it became clear that the KLM was nearing takeoff speed, Captain Grubbs said, "That son of a (expletive) is coming straight at us!" First Officer Robert Bragg, at nearly the same moment can be heard saying, "Get off! Get off! Get off!"
Attempting to avoid a collision, Captain Grubbs desperately attempted to steer off the runway -- whilst seeing the KLM's landing lights fast approaching.THE COLLISION
By the time the KLM crew saw that the Pan Am was still on the runway, it was too late. The KLM jet was traveling too fast to stop. In desperation, Captain van Zanten prematurely lifted his aircraft to avoid the other jet by climbing away. However, with tens of thousands of pounds worth of new fuel in its tanks, the KLM jet was too heavy.
Although the nose cleared the Pan Am jet, the KLM's engines, lower half of its fuselage, and landing gear struck the upper half of the Pan Am fuselage at approximately 160 miles per hour. The collision tore apart the center of the Pan Am plane, almost directly above the wing. The KLM's right engines crashed through the Pan Am's upper deck right behind the cockpit.
The Dutch airliner remained airborne for a few seconds, but the crash had sheared off two of the jet's engines. Further, the remaining two engines ingested debris from the Pan Am plane -- forcing the KLM to stall, roll sharply and hit the ground. According to the official investigation, the airliner slid approximately 1,000 feet down the runway after hitting the Pan Am. The full load of new fuel ignited immediately.THE AFTERMATH
:Of the 396 people aboard the Pan Am jet, only 61 survived the accident. There were no survivors from the KLM. In all, 583 people died in the collision -- making it the deadliest accident in aviation history, a distinction that still stands today.
Immediately after the crash, the engines of the Pan Am jet continued to run at takeoff power -- creating a menacing and frightening noise for the surviving passengers and crew. After a few minutes, the engines began to disintegrate and spewed shards of metal indiscriminately toward the survivors. A flight attendant died while standing on the airfield -- having survived the crash and escaped the burning plane, only to be killed by flying shrapnel from the engines.
The sounds of the collision could be heard across the airport. If a single 747 crashes, it's a substantial incident. Here, controllers realized, they were dealing with two 747s that crashed.
Emergency vehicles and personnel flooded the runway -- which was still covered in fog. Responders attended first to the KLM jet, initially unaware that the Pan Am jet was also ablaze further up the runway.
The disaster at Tenerife ultimately triggered a number of changes across the aviation industry. Officials introduced a list of standard phrases to be used in traffic communication, in an effort to avoid critical misunderstandings that doomed the victims at Tenerife. Also, cockpit procedures and routines were also modified.
Subsequent investigations placed much of the blame on the KLM jet -- and specifically Captain van Zanten, who despite his wealth of experience, committed a series of severe violations during his attempt to take off.
Much was also made of the captain's decision to refuel at Tenerife -- instead of Las Palmas, as was initially planned. Refueling at Tenerife had three particularly grave consequences for the disaster. First, the KLM and the fueling truck blocked the runway for 35 minutes, allowing thick fog to settle in and hamper visibility. Second, the fuel added 40 tons of weight to the 747, bogging the aircraft down when Captain van Zanten attempted to clear the Pan Am by flying over it. And third, all of the extra fuel created an even larger fire once the KLM jet crashed on the runway. A smaller fire, critics note, may have allowed some passengers or crew aboard the Dutch airplane to survive.MORE:
-The Tenerife disaster