Tenerife airport disaster
The KLM captain wanted to takeoff quickly so that he could return to Amsterdam as soon as possible. Because of a radio heterodyne, this made him misunderstand a partly garbled transmission into thinking that he was cleared by the Air Traffic Controller to takeoff, and so he began his takeoff roll, not knowing that the Pan American 747 was still on the runway.. At that time, the Tenerife North Airport did not have ground radar, so the controllers could not know that the KLM flight was taking off.