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,[1][2] when the plane crashed into El Carbón, a mountain in the Sierra Madre Occidental mountain range northwest of Mexico City, instantly killing everyone on board.

Spanish newspaper El País reported that there were at least 20 foreigners on board, with eight from France, six from the United States, four from Sweden, and two from Canada.

[6] The plane was commanded by 35-year-old Captain Carlos Alberto Guadarrama Sixtos, who joined Mexicana in December 1971, clocked a number of 6,328 hours of total flying experience.

The first officer was 34-year-old Philip Louis Piaget Rhorer, hired by Mexicana in April 1980, he had a little over 1,769 total flying hours.

[1] : 11–12 The wife of Captain Guadarrama, Graciela Flores, who was a retired flight attendant, and their son and daughter were among the 159 passengers on board.

[8] Mexican art director Agustín Ituarte, who was participating on the filming of the movie Predator, was also onboard the flight.

Realizing this, Captain Guadarrama ordered First Officer Piaget to increase the thrust and accordingly the lever was moved forward to 100%.

Hearing such warning, the pilots decided that they needed to decrease their altitude and began to follow the correct procedure.

[12][1]: 3–8 As they were trying to figure out the emergency, a flight attendant came to the cockpit and reported that there was a fire inside the cabin, which had originated from the floor below.

As the fire grew uncontrollably, the tail section of the aircraft, including all three engines, eventually separated in flight.

After multiple failed attempts to call the crew, Flight 940 was declared as missing and emergency personnel were dispatched to search the plane.

They eventually received calls from local residents that an aircraft had crashed in the foothills of the mountain range near a place known as San Miguel el Alto, in the municipality of Maravatio, Michoacan.

[14] The crash site was found within hours, as an ATC worker in Morelia reported seeing a smoke column just minutes after they had lost contact with the flight.

Mexican authorities confirmed that, based on the communication made between the pilots and ATC, a depressurization had occurred in-flight.

Meanwhile, the Mexican Association of Travel Agents stated that they did not believe that the aircraft had been brought down, adding reassurance that the tourism industry of the nation would not be affected by the disaster.

[8] However, just days after the crash, two militant groups from the Middle East issued a written statement claiming that they had bombed Flight 940.

[19] However, UPI reported that Mexicana had issued an "internal memorandum" for all personnel regarding significant changes in handling baggage and cargo following suspicions that Flight 940 had been brought down by on-board explosives.

[21] Then-President of IFALPA, Reg Smith, called for leaders to enact sanctions against countries that provided sanctuary to terror groups or encouraged hijacking commercial airlines.

The Ministry of Communication added that the explosion might have severed the hydraulic and fuel lines of the aircraft, causing the fire to grow.

As the aircraft was US-made, representatives from the United States National Transportation Safety Board (NTSB), Federal Aviation Administration, Boeing and Pratt & Whitney would be sent to Mexico to assist with the investigation.

Other than the broom straws were metallic spray, a burn mark that was caused by contact between molten aluminium and the cold airframe structure.

Witnesses' reports of smoke seen trailing from the tailplane further confirmed that the chimney draft effect was occurring during the flights' final minutes.

[1] : 27–29 As it was located in a difficult-to-access area, added with the chimney draft effect, the fire grew at an incredibly fast rate.

The melted airframe, which was located at the back of the aircraft, subsequently caused the structure to fail and the tailplane to completely separate.

[1]: 27–36 Investigators thought that the fire likely had originated from the left wheel well, as indicated by the distribution of the wreckage and findings found during visual inspection of recovered aircraft components.

The left landing gear apparently had suffered massive drag forces during the take-off, which caused temperature to rise dramatically.

This was supported by the cockpit voice recording, in which Captain Guadarrama was heard saying that the aircraft felt heavier and that the take-off was taking longer than usual.

[1]: 3–8, 33–37 A closer examination of the brake assembly revealed that at a certain point the tire had been inflicted with overheating, with heat reaching more than 871 degrees Celsius, a temperature that metals and other components could not withstand.

As there was barely minimum ventilation in the wheel well, the temperature continued to rise as hot air released from the tire could not be drained out of the aircraft at a sufficient pace.

[1] About a year after the crash, the U.S. FAA released an Airworthiness Directive[28] requiring the use of dry nitrogen (or other gases shown to be inert) when filling the tires on braked wheels of most commercial airliners.