On June 23, 1985, a bomb exploded on an Air India Boeing 747, killing as many as 329 people. It was the heaviest terrorist attack on any aircraft in history in terms of the number of victims, and it was also the first bomb activated on large Boeing 747 aircraft (Jumbo Jet).
The bomb blew up a Boeing 747 over the Atlantic Ocean, about 200 kilometers southwest of the coast of Ireland. It was an Air India flight from the Canadian city of Toronto to New Delhi, with a scheduled landing in London, but the plane was destroyed before it even managed to land in London. At the time of the explosion, there were 307 passengers and 22 crew members on board, and all but one were killed (it was a detonation at an altitude of as much as 9,400 meters).
Most of the passengers were Canadian nationals of Indian descent, and it is believed that the explosive was planted in retaliation for the Indian attack on the famous Golden Sikh Temple in Amritsar. That attack (Operation Blue Star) had taken place in June of the previous year on the orders of Indian Prime Minister Indira Gandhi. The Prime Minister was also assassinated in retaliation, by her bodyguards Siki, in October 1984. The remains of 132 people were found on the surface of the sea. It was also a huge tragedy for Canada, as most of the dead were its citizens (it was the largest mass murder in Canadian history).