On July 8, 1965, Canadian Pacific Air Lines Flight 21, a Douglas DC-6B carrying 52 people, exploded in mid-air near 100 Mile House, British Columbia, killing everyone aboard. The aircraft was on a scheduled domestic flight from Vancouver to Whitehorse, Yukon, with planned stops in Prince George, Fort St. John, Fort Nelson, and Watson Lake. At some point during the flight's ascent, an explosion tore through the cabin with such violence that the plane broke apart and fell to the remote British Columbia wilderness, scattering wreckage across the forest floor.

Investigators who examined the debris field determined quickly that the destruction matched the signature of an onboard bomb rather than mechanical failure or weather. The force and pattern of the explosion left no doubt: someone had placed an explosive device aboard the aircraft before takeoff. The inquest that followed confirmed this finding, making Flight 21 the first confirmed case of aviation sabotage in Canadian history. Yet despite intensive investigation, authorities could never definitively identify the perpetrator or establish a clear motive for the attack.

The disaster shocked Canada and raised urgent questions about airline security that remained largely unanswered at the time. In 1965, airport screening procedures were minimal by modern standards, and there was no comprehensive system for detecting explosives or vetting passengers and baggage. The mystery surrounding Flight 21 lingered for decades, becoming one of Canada's most infamous unsolved crimes. While other sabotage cases would eventually yield arrests and confessions, this bombing remained cold, haunting investigators and the public imagination as a reminder of aviation's vulnerability to deliberate human destruction.