1. KLM and Pan Am Tenerife air crash, also known as canary air crash. It happened on the evening of March 27th. 1977. At Los Rodeo Airport in the Canary Islands, two Boeing 747s collided at high speed on the runway, killing as many as 583 passengers and crew on both planes. If the casualties on the ground are not considered, this air crash is still the deadliest and the aviation accident with the largest number of casualties before the 9 1 1 incident.
2. JAL Boeing 747SR crashed and flew from Tokyo to Osaka on August 1985. A terrible mechanical failure killed 520 people. Boeing 747SR crashed into a mountain and made history on two ridges in Japan, which is really unprecedented.
It is a pity that these two kinds of air crashes could have been avoided unexpectedly.