A KLM 747 and a Pan Am 747 were diverted to Tenerife after a bomb exploded at their destination airport in Spain. While waiting for the mainland to reopen, a fog settled in on Tenerife. The Airport there did not have ground radar, and could only tell where aircraft were based on radio communications. The airport had aircraft parked on the taxiways, requiring each aircraft to taxi down the runway to prepare for take off. Neither aircraft could see the other, nor could the controllers in the tower. The tower couldn't even see the runway! The KLM flight misunderstood the ATC, thinking they had permission to take off, even though there was no such transmission from the tower specifically giving permission. A simultaneous transmission from the Pan Am 747 squelched KLM's ability to hear the tower. Pan Am's transmission was that they were still on the runway, and to hold KLM. Apparently, KLM didn't get that transmission either. There was a final series of transmissions between the tower and Pan Am. The tower telling Pan Am to notify them when they were clear of the runway. The KLM flight engineer asked if the Pan Am jet was clear, and the Captain said "Oh yes." and continued the run.
Pan Am spotted the landing lights approaching and made a hard left turn onto the grass to avoid the collision. KLM attempted to rotate too early and attempted to climb out. KLM's angle of attack allowed the nose gear to clear Pan Am's fuselage, but the rest of the aircraft struck the Pan Am jet on the right side at 160mph. Both aircraft were completely destroyed.
all 234 passengers and 15 crew on the KLM flight were killed in the collision, but of the 326 passengers and 9 crew of the Pan Am flight, 56 passengers and 5 crew survived.