Mexicana de Aviación Flight 940

1986 aviation accident

Mexicana de Aviación Flight 940, operated by Mexicana de Aviación, was a scheduled international flight from Mexico City to Los Angeles with stopovers in Puerto Vallarta and Mazatlán on March 31, 1986, utilizing a Boeing 727 200 registered as XA MEM, when the plane crashed into El Carbón, a mountain in the Sierra Madre Occidental mountain range northwest of Mexico City, killing everyone on board. With 167 deaths, the crash of Flight 940 is the deadliest aviation disaster ever to occur on Mexican soil, and the deadliest involving a Boeing 727.

At 09:05, fifteen minutes after takeoff, an explosion rocked the fuselage. Captain Guadarrama and the crew in the cockpit, realizing that the plane was shaking too much, declared an emergency and asked to return to Benito Juárez International Airport for an emergency landing. The airport was prepared for the landing. However, the aircraft crashed into El Carbón mountain near the town of Maravatío, Michoacán, broke in two and burst into flames.

Initially, two Middle Eastern terrorist groups claimed responsibility for this crash, along with the bombing of TWA Flight 840, which occurred just two days later. An anonymous letter signed by those groups claimed that a suicide mission had sabotaged the plane in retaliation against the United States. However, sabotage was later dismissed as a cause of the crash. The investigations were carried out by the U. S. National Transportation Safety Board and Mexican aeronautical authorities, who found that the cause of the accident was that a LH main landing gear tire was filled with compressed air, instead of nitrogen. requiring the use of dry nitrogen (or other gases shown to be inert) when filling the tires on braked wheels of most commercial airliners. The crash remains the deadliest airline disaster in Mexican history and is the world's deadliest air disaster involving the Boeing 727. The cause of the in flight fire is believed to be the rupture of fuel lines by the exploding tire.