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, instantly killing everyone on board. With 167 deaths, the crash of Flight 940 is the deadliest aviation disaster ever on Mexican soil, and the deadliest involving a Boeing 727.
An inquiry was opened by the Mexican government with additional assistance from the National Transportation Safety Board. The investigation concluded that the crash was caused by an explosion that originated in the wheel well. The wheel had overheated during the take-off run as it had suffered high drag on the ground, which was caused by faulty brakes. Fire ensued as the explosion ignited the fuel and hydraulic liquids, causing the fire to quickly grow. The aircraft eventually suffered structural failure due to the severity of the fire and eventually crashed onto the side of the mountain.
Aircraft.
The aircraft involved in the crash was a Boeing 727-200 with a msn number of 22414. Built in 1981, it was initially planned to be delivered to Braniff International Airways before it was sent to Mexicana The aircraft was eventually named "Veracruz". The aircraft had accrued a total flying hours 13,675 hours and total flight cycles of 10,252 cycles. The last major maintenance check was conducted last year. The engines, three JT8D-17R from Pratt &amp; Whitney, were in good condition.
Passengers and crew.
The aircraft carried a total of 167 passengers and crews. Of those, a total of 147 passengers (139 passengers and 8 crew members) were from Mexico. 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. The French embassy later confirmed that at least 8 passengers of its nationals were on board, all of whom were from a single family. Swedish Embassy stated that one of its staff and her children were on board the flight. According to "UPI", there were 22 children aboard the flight.
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. The second officer, Ángel Carlos Peñasco Espinoza, was hired by Mexicana in 1982, and had a total of 1,142 total flying hours. The crew of eight included five flight attendants. 
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. They had planned to travel across the United States when they arrived. Flores had survived the crash of Mexicana de Aviación Flight 801 in 1969. Also among the passengers was Guillermo Sánchez, the cousin of former Mexican footballer Hugo Sánchez. American tennis player Derrick Rostagno was also booked on the flight, which he had booked as a connecting flight, but he chose to stay in Mexico City to play a match.
Crash.
The aircraft had just returned from Chicago at 07:12 a.m as Flight 185. The flight was uneventful; however, the crew of said flight noted their concerns regarding the aircraft's components. Those include a missing rod on the brake assembly, altitude differences, strong shaking, and two other issues. The problems were eventually rectified by personnel in Mexico City, and the aircraft was allowed to be put into service.
Flight 940 was scheduled to take off from Mexico City International Airport en route to Los Angeles International Airport with scheduled stopovers in Puerto Vallarta and Mazatlán. With 159 passengers and 8 crew members, the aircraft taxied onto Runway 05 left. At around 08:50 local time, the aircraft began its take-off run. However, while rolling on the runway the crew felt that the aircraft was heavier than usual and that it didn't pick up speed as much as expected. Realizing this, Captain Guadarrama ordered First Officer Piaget to increase the thrust and accordingly the lever was moved forward to 100%. The aircraft eventually took off approximately 11 seconds later than the previous estimation.
At 09:05, fifteen minutes after takeoff, the aircraft was climbing to an altitude of 29,400 feet when an explosion rocked the fuselage. The explosion was large enough that it broke the cabin floor, causing a loss of cabin pressure and prompted the oxygen masks to drop. Multiple alarms, including the depressurization alarm, began to blare in the cockpit. Hearing such warning, the pilots decided that they needed to decrease their altitude and began to follow the correct procedure. The crew requested the ATC for lower altitude while attempting to find out the situation they were facing.
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. Smoke was seen entering the cabin, and the cabin temperature, particularly at the back fuselage, became hot as the fire grew larger. Passengers seated at the back were moved to the front to avoid the fire. The crew contacted ATC and asked for an emergency landing in Mexico City, which was eventually approved. As the crew tried to divert to Mexico City, the aircraft became harder to control. The fire had grown so large that smoke could be seen from outside as it was trailing from the tailplane.
The crew reported that they kept losing altitude. Meanwhile, the intense heat from the fire eventually melted a large portion of the back fuselage. The structural integrity of the fuselage began to fail due to the intense fire and thick smoke began to roam inside the cabin. The fire then managed to enter the passenger area, causing panicked passengers to rush towards the front. The fire then severely damaged the control cables, making the aircraft harder to control. As the fire grew uncontrollably, the tail section of the aircraft, including all three engines, eventually separated in flight. The aircraft broke apart into two pieces and nose dived. The tail section crashed into a hill, while the front portion slammed into a ravine. The aircraft struck El Carbón mountain near the town of Maravatío, Michoacán, and burst into flames. All 167 passengers and crew were killed upon impact.
Response.
Immediate aftermath.
The aircraft lost contact just 3 minutes after it made a request to return to Mexico City. 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. Eyewitnesses reported details of the crash to authorities and the local police and the Mexican army were dispatched to the crash site.
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. The wreckage was found scattered among the Sierra Madre Occidental ranges since the aircraft broke up in mid-air. The tail section was found on the foothill with at least 20 bodies found inside, while the front portion, which constituted the majority of the aircraft and occupants, was found near a crevice. Flames could be seen still erupting from the crash site. 
At least 500 personnel were dispatched for the recovery efforts, most of whom were soldiers and Mexican Red Cross. Local volunteers were also assisting. However, the crash site was remote and difficult to reach. The nearest road was located at least 14 km from the site, and rescuers had to walk by foot. Some of the team were flown by helicopter, but due to the vegetation and hilly terrain, they still had to walk on foot. By the time they reached the site, the wreckage was still smouldering. Firefighters managed to douse the flames approximately eight hours after the crash. Meanwhile, multiple reports of looting by peasants and local officials began to emerge as well.
Due to the remoteness of the site and hilly terrain, rescuers had to use mules and donkeys to move the bodies from the crash site. The victims would be carried to Maravatio and then flown to Morelia before being finally flown to Mexico City. The country's forensic medical service, SEMEFO, stated that bodies would be handed over by 1 April, while the bodies of non-Mexican victims of the crash would be handed over to their respective embassies. Meanwhile, families of the victims were asked to gather at Mexico City's morgue to identify the victims.
Mexicana de Aviación established a special office in Mexico City for the families of the victims. The airline later added that the families would be compensated, including victims' repatriation and insurance claims from relatives. Mexicana Airlines director Manuel Sosa de la Vega was eventually ordered by the Mexican Congress to testify following charges that the airline had neglected maintenance and safety standards, allegations which the airline and the mechanics and ground crew union denied.
By 1 April, all of the bodies had been recovered from the crash site. A total of 109 bodies were recovered on that day, and all were flown to Mexico City on four flights. Rescuers also managed to retrieve the aircraft's FDR and CVR, which would be transported to Mexico City for analysis.
Controversy.
Following reports that the aircraft had suffered an in-flight decompression, speculations began to run wild. Mexican authorities confirmed that, based on the communication made between the pilots and ATC, a depressurization had occurred in-flight. Airline officials refuted claims that Flight 940 had been bombed. 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.
However, just days after the crash, two militant groups from the Middle East issued a written statement claiming that they had bombed Flight 940. The groups, identified as Abu Nidal Organization and Egypt Revolutionary Organization, claimed responsibility for the crash of Flight 940. In the statement, both groups stated that the bombing was carried out "in retaliation for the imperialist American military invasion of the Libyan Popular Arab Republic and in revenge for the fascist, Zionist, U.S. raid on Mieh Mieh camp in Southern Lebanon". The purported perpetrator was named as Mohammed Mustafa Muhsin Al-Mashoor. Lebanese intelligence, however, confirmed that they had never received any reports of plans from the group to attack commercial airlines. Officials opined that the statement might have been made for propaganda.
Despite initial statements made by officials denying that the aircraft had been bombed, multiple pilots from Mexicana challenged the statement after they managed to get a readout of the aircraft's Flight Data Recorder. A total of 10 pilots claimed that the crash might have been part of a life insurance scam from a disgruntled passenger, as evidenced by the first audible explosion and the second larger explosion, which directly caused the aircraft to break up. Both airline and government officials condemned the accusation, calling them premature. 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.
Coincidentally, two days after the crash of Flight 940, a Trans World Airlines (TWA) Boeing 727-200 was bombed by the Abu Nidal Organization, the same group that had claimed responsibility for the Mexicana crash. In response to the TWA bombing and the alleged downing of Flight 940, the International Federation of Airline Pilots Associations (IFALPA) issued a statement calling for strengthening the security of flights. Some even proposed to boycott flights due to the perceived lack of security oversight. 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.
Nearly two months after the crash, the Mexican government announced the possible cause of the in-flight decompression. Preliminary data from the flight