Air India Flight 182 was a passenger flight operating on the Montreal–London–Delhi–Bombay route, that on 23 June 1985, disintegrated over the Atlantic Ocean as a result of an explosion from a bomb 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 24 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]