40 Years ago today: On 26 November 1979 a Pakistan International Boeing 707 crashed 125km from Jeddah following an inflight fire, killing all 151 occupants.

Date:Monday 26 November 1979
Time:02:04
Type: Boeing 707-340C
Operator:Pakistan International Airlines – PIA
Registration:AP-AWZ
C/n / msn:20275/844
First flight:1970
Total airframe hrs:30710
Engines:Pratt & Whitney JT3D-3B
Crew:Fatalities: 11 / Occupants: 11
Passengers:Fatalities: 145 / Occupants: 145
Total:Fatalities: 156 / Occupants: 156
Aircraft damage:Destroyed
Aircraft fate:Written off (damaged beyond repair)
Location:48 km (30 mls) N of Taif (   Saudi Arabia)
Crash site elevation:915 m (3002 feet) amsl
Phase:En route (ENR)
Nature:International Scheduled Passenger
Departure airport:Jeddah International Airport, Saudi Arabia
Destination airport:Karachi International Airport (KHI/OPKC), Pakistan
Flightnumber:PK740

Narrative:
Flight PK740 departed Jeddah at 01:29 for a flight to Karachi. The aircraft was climbing to FL370 when, at 01:47, a stewardess reported a fire near the aft cabin passenger door. The crew started a descent from FL300 and were cleared to descend to 4000 feet. Following a mayday call at 02:03 nothing more was heard from the flight. The aircraft crashed in a level rocky area at an elevation of 3000 feet and burst into flames

Probable Cause:

PROBABLE CAUSE: “An in-flight fire in the cabin area which, through its intensity and rapid extension, resulted in panic among the passengers and smoke in the cockpit, eventually incapacitating the flight crew. The cause of the cabin fire was not determined.”
It was considered that the origin of the cabin fire could have been a leaking gasoline or kerosene stove, carried aboard by Haj pilgrim passengers. Pressure differential could have caused a poorly sealed gasket to leak fuel.
A second possibility is an electrical fire, but the rapid extension of the fire was considered difficult to explain because of the electrical circuit protection devices of the Boeing 707. Sabotage was considered as another possibility, but no evidence of use of an incendiary device was found.