On March 28 1977, a terrorist bomb exploded at Las Palmas airport in the Canary Islands, and as a result a number of planes were diverted to Los Rodeos airport on Tenerife.
Several hours later, a KLM 747 jumbo jet attempted to take off, unaware that a Pan Am 747 was on the same runway. The KLM plane tore the top off the Pan Am jet, and managed to climb a short distance before crashing further down the runway. 274 out of 335 people on the Pan Am jet died. There were no survivors on the KLM jet. A total of 583 people died in the collision, making it the worst air disaster in history.