Air India Flight 182 was a passenger flight operating on the Montreal–London–Delhi–Mumbai route, that on 23 June 1985, disintegrated over the Atlantic Ocean as a result of an explosion from a bomb allegedly planted by Canadian Sikh terrorists.[1][2][3] It was operated using a Boeing 747-237B registered VT-EFO. The incident happened en route from Montreal to London at an altitude of 31,000 feet (9,400 m). The remnants of the aircraft fell into the sea approximately 190 kilometres (120 miles) off the coast of Ireland, killing all 329 people on board, including 268 Canadian citizens, 27 British citizens, and 22 Indian citizens.[4] The bombing of Air India Flight 182 is the worst terrorist attack in Canadian history, the deadliest aviation incident in the history of Air India and was the world's deadliest act of aviation terrorism until the September 11 attacks in 2001.[1][5][6] The mastermind behind the bombing was believed to be Inderjit Singh Reyat, a dual British-Canadian national, who pleaded guilty in 2003[7][8] and Talwinder Singh Parmar, a Canadian Sikh separatist leader, who was one of the key individuals associated with the militant group Babbar Khalsa.[9]

The plan's execution had transnational consequences and involved citizens and governments from five nation states. Babbar Khalsa, a Sikh terrorist and Khalistani separatist group, was implicated but not confirmed to be responsible for the bombing.[10] Although a handful of people were arrested and tried for the Air India bombing, the only person convicted was Inderjit Singh Reyat, who pleaded guilty in 2003 to manslaughter.[11][12] He was sentenced to fifteen years in prison for assembling the bombs that exploded on board Air India Flight 182 and at Narita.[13][14]

The subsequent investigation and prosecution lasted almost twenty years. This was the most expensive trial in Canadian history, costing nearly C$130 million. The two accused, Ripudaman Singh Malik and Ajaib Singh Bagri, were both acquitted and found not guilty.

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.[15]