Air India Flight 182 was an Air India flight operating on the Montreal–London–Delhi–Mumbai route. On 23 June 1985, it was operated using Boeing 747-237B registered VT-EFO. It disintegrated in mid-air en route from Montreal to London, at an altitude of 31,000 feet (9,400 m) over the Atlantic Ocean, as a result of the explosion from a bomb planted by militant, Canadian-Sikh separatists. The remnants of the airliner fell into the ocean approximately 190 kilometres (120 miles) west-southwest of the southwest tip of Ireland, killing all aboard: 329 people, including 268 Canadian citizens, 27 British citizens and 24 Indian citizens. The bombing of Air India Flight 182 is the largest mass killing in Canadian history, Canada's worst terrorist attack, the deadliest aviation incident in the history of Air India and was the deadliest act of aviation terrorism until the September 11 attacks in 2001.The attack was a part of a larger transnational terrorist plot and had included two attempted plane bombings. The first bomb was meant to explode aboard Air India Flight 301 which was scheduled to takeoff from Japan but exploded before it was loaded onto the plane. The second bomb planted aboard Air India Flight 182 in Canada was successful. Though it was eventually determined that both the plot and the bombs, which had been hidden inside luggage, had originated from Canada, its execution had transnational consequences and involved citizens and governments from five different nation states. The Babbar Khalsa separatist group was implicated in the bombings.The bombing of Air India Flight 182 coincided with the Narita Airport bombing. Investigators found the two plots were linked and eventually concluded that those responsible were aiming for a double aircraft bombing. However, the bomb at Narita exploded killing two baggage handlers before it was loaded onto the plane due to the perpetrators failing to take into account that Japan does not observe daylight saving time.

Although a handful of members were arrested and tried for the Air India bombing, the only person successfully convicted was Inderjit Singh Reyat, a dual British-Canadian national and a member of the International Sikh Youth Federation (ISYF), who pleaded guilty in 2003 to manslaughter. He was sentenced to fifteen years in prison for assembling the bombs that exploded on board Air India Flight 182 and at Narita.The subsequent investigation and prosecution lasted almost twenty years. This was the most expensive trial in Canadian history, costing nearly C$130 million. The Governor General-in-Council in 2006 appointed the former Supreme Court Justice John C. Major to conduct a commission of inquiry. His report, which was completed and released on 17 June 2010, concluded that a "cascading series of errors" by the Government of Canada, the Royal Canadian Mounted Police (RCMP), and the Canadian Security Intelligence Service (CSIS) had allowed the terrorist attack to take place.