Pakistan International Airlines Flight 740

The aircraft involved was a nine-year-old Boeing 707-340C with serial number 20275 and serial 844. It was built in 1970 and on July 30 made its first flight. Ten days later, on 10 August, it was delivered to Pakistan International Airlines (PIA) and was registered as AP-AWB. It was re-registered as AP-AWZ in 1972 after being leased for several months to another airline. The aircraft had 30,700 flight hours at the time of the crash.[1][2]

The airliner operated as flight 740 from Jeddah to Karachi, during which it carried pilgrims returning from the Hajj. There were a total of 156 people on board, 11 crew members and 145 passengers. At 01:29, flight 740 departed from Jeddah and began to climb to the planned flight level (FL) of 37,000 feet (11,000 metres). The first warning of an emergency came at 01:47, 21 minutes after takeoff, when a flight attendant informed the pilots that a fire had started in the rear of the cabin. After reporting to air traffic control (ATC) about the situation on board and beginning an emergency descent from its current altitude of 30,000 feet (9,100 metres), the crew received permission to descend to a height of 4,000 feet (1,200 metres). The pilot radioed a request to return to Jeddah because smoke was coming into the cabin and cockpit. At 02:03 the crew sent a distress signal. The Jeddah control tower heard the pilot shout "Mayday! Mayday!" before the radio went silent.[3] Approximately one minute after this transmission, the aircraft crashed into an area of rocks located 48 kilometres (30 miles; 26 nautical miles) north of the city of Taif and at an altitude of 3,000 feet (910 metres). All 156 people on board died. The accident remains, to date, the third-deadliest plane crash on Saudi Arabian soil and the third-deadliest Boeing 707 crash.[2]

The cause of the accident was an in-flight fire in the cabin area, which, through its intensity and rapid extension, eventually incapacitated the flight crew. The cause of the cabin fire was not determined. The most likely version is that there was a gas leak or kerosene from one of the pilgrims' stoves. The fuel leakage may have been a result of the decrease in cabin pressure. A malfunction in the electrical circuits was also considered as an ignition source, but could not be confirmed because of the design of the aircraft's electrical systems and protection devices. Terrorism was ruled out as a cause, as there was no evidence that incendiary devices were used.[2]

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Accident description at the Aviation Safety Network