100 Mile House, BC Plane Explosion, July 1965
Canadian Pacific Flight 21 was a domestic flight from Vancouver (YVR) to Whitehorse (YXY) via Prince George (YXS), Fort St. John (YXJ), Fort Nelson (YYE) and Watson Lake (YQH).
At 14:42, the DC-6 "Empress of City of Buenos Aires" took off on an instrument flight plan for Prince George, via Victor 300 and Blue 22 airways.
En route, at 15:29 the crew reported to Vancouver ATC Centre that they had passed Ashcroft at 16,000 feet. They were estimating William Lake at 15:48.
At 15:38 hours, Vancouver Centre called Flight 21 and did not receive a reply. About two minutes later, three "Mayday" calls were heard by Vancouver Centre. An explosion had occurred in the left aft lavatory. Smoke trailed the aircraft and the tail separated from the fuselage. The main portion of the wreckage assumed a nose down attitude and spiralled to the left until it crashed into a wooded area.
PROBABLE CAUSE: "Explosion of a device which resulted in aerial disintegration."
Also, from en.wikipedia.org:
A coroner's inquest concluded "an explosive substance foreign to the normal contents of the aircraft" caused the crash. A witness on the ground saw the tail of the aircraft separate from the fuselage and debris trail out behind the aircraft. The debris turned out to be the bodies of passengers forced out by the depressurization of the aircraft. The fuselage was consumed by fire where it fell but the tail, found a half kilometre away, was not. Rescue crews reached the crash site while the fire continued to burn but no survivors were found. Crash investigators found traces of acid that led them to believe a bomb in the lavatory was involved. Traces of potassium nitrate and carbon, consistent with a "low-velocity explosion"
were found. Gunpowder or stumping powder causes a low-velocity explosion. The explosion damaged bulkheads in the lavatory, severed pipes in the tail and tore a metre-wide hole in the side of the fuselage. The Royal Canadian Mounted Police investigation focused on four passengers although none was a suspect. Charges were never laid. The source of the explosion remains unknown.