Mexicana flight 940, a Boeing 727, crashed near Las Mesas, Mexico, following an in-flight fire, killing all 167 occupants. Flight MX940 took off from Mexico City (MEX) at 08:40 for a flight to Puerto Vallarta (PVR), Mazatl n (MZT) and Los Angeles (LAX). The left main gear brake was overheated during the takeoff run. When the aircraft had reached FL310 the heat caused a tyre on the left hand main gear to explode. Fuel and hydraulic lines were ruptured and electrical cables severed resulting in a cabin decompression. An emergency was declared, but spilt fuel ignited and caused a massive fire on board. Control was lost and the aircraft crashed into a mountain in the Sierra Madre, at an elevation of 9000 feet. It was found that the tire had been serviced with air rather than nitrogen. The air, under high temperature and pressure, resulted in a chemical reaction with the tire itself. This led to a chemical explosion of the tire. Probable Cause: Failure in the brake system caused the number one assembly to drag, generating high temperatures that, when transmitted to the hub (wheel) and the air enclosed in the tires, resulted in the explosion of tire number one, fragmenting hub number two, breaking the fuel line that supplied engine number one and hydraulic lines, causing an intense fire that destroyed the lower rear part of the fuselage, weakening the lower structure, leading to the detachment of the tail unit and consequently the loss of control of the aircraft.