On This Day in 1977...

...happened the world's worst aviation disaster all because of a 4 second hiss in communication.
583 people lost their lives when two Boeing 747s collided on the runway at Los Rodeos Airport in Tenerife, Spain.

Both, PanAm 747 and KLM 747, were headed for the bigger Las Palmas airport but a terrorist threat had forced it to be closed and instead they had to land at Los Rodeos.

At 2:30 PM GMT, the aircrafts are informed that the Las Palmas airport has re-opened. To make up for lost time (and reduce traffic at the airport) the control tower suggests the PanAm captain to taxi just behind the KLM 747. The PanAm captain accepts.

Two hours later, both are backtracking the 3400 meters runway at low speed. The KLM will move towards the end of the runway from where it will report for take off. The PanAm one shall exit the runway at the third taxiway in order to let the KLM aircraft take-off. In the meantime the weather has worsened and the visibility is down to a few hundred metres.

At 4:55 PM KLM reaches the end of the runway. The PanAm 747 crew has just passed the third taxiway without seeing it. They saw the first one, they missed the second one, and they are now passing the third one thinking it is the second one. They are going to the fourth one.

The visibility improves momentarily and the KLM Captain doesn't want to miss this opportunity, he is already in stress as the Dutch regulations don't permit the pilots to fly beyond their hours quotas; if he doesn't take off soon both he and KLM will be in trouble. The KLM gets the clearance, but is not allowed to take off yet. However, the captain, in his hurry starts increasing the throttle. He seems to have forgotten that another aircraft is still taxiing on the runway. The stressful situation is probably the cause of this mistake.

5 :06 :13 (Captain) : We gaan. (We're going)
5 :06 :19 (Ténérife control tower) : OK
At the same time, the Panam first officer is talking :
5 :06 :19 (PanAm first officer) : No .. eh...

The controller now is in doubt. He reminds the KLM captain that he is not allowed to take-off.
5 :06 :20 (Ténérife control tower) : Stand by for take-off, I will call you.
5 :06 :20 (PanAm first officer) : And we're still taxiing down the runway...

The last two messages have been said at the same time. Consequently, they just became a long 4 seconds shrill in the KLM cockpit. The KLM increases its speed. 1500 meters further, the PanAm is still taxiing on the runway.

The PanAm captain sees landing lights of KLM Boeing at approximately 700m in the fog.

5 :06 :41 (PanAm captain) - (screaming) : He's coming...look...this son of bitch is coming!
5 :06 :41 (PanAm first officer) - (screaming)

The PanAm crew set full throttle to leave the runway ASAP to its left. But it is too late. The KLM captain sees the PanAm jumbo on the runway.

5 :06 :47 (KLM captain) : Oh shit!

The KLM is moving at about 270 km/h. The captain tries to take off and pass over the other aircraft. The nose climbs, the tail strikes the runway making sparks. The aircraft climbs from 1 meter, but it is not enough.
Both aircrafts collide. The forward landing gear wheels strike the right side of the PanAm 747, tearing the fuselage. The left wing cut the vertical stabilizer at the rudder level. Right wing fuel tanks are torn and the fuel catches fire.
The KLM 747 climbs slightly but it is completely dislocated and it crashes. There is no survivor.
In the PanAm 747, a few people escape from the burning plane. 64 people (including the captain all the people in flight deck) survived. All 251 passengers on the KLM and 332 on PanAm lost their lives.

Saw a documentary on this accident on National Geographic a few weeks ago - just left me stunned.

Here is a link on Wikipedia detailing the chain of events and the aftermath of the accident.


Also a graphical representation of what happened, also from Wikipedia