Air India Flight 182 bombing

Who: The 2010 Canadian commission of inquiry said Talwinder Singh Parmar and the Babbar Khalsa, a Sikh separatist group, were behind the attacks. ThePrint notes that Parmar was never convicted and was killed by Indian security forces in 1992. The only person convicted was Inderjit Singh Reyat, who built the bombs and was convicted of manslaughter and perjury. Ripudaman Singh Malik and Ajaib Singh Bagri were tried and acquitted in 2005.

What: On 23 June 1985 Air India Flight 182, a Boeing 747 flying from Canada to Delhi by way of London, was destroyed by a bomb and fell into the Atlantic off the southwest coast of Ireland. All 329 people aboard were killed. ThePrint lists 268 Canadians, mostly of Indian descent, 27 Britons and 24 Indians, which comes to 319, so about 10 were of other nationalities. Wikipedia's table, citing a CBC list, counts 307 passengers and 22 crew: 268 Canadians, 27 Britons, 22 Indians, 10 Americans and 2 of undetermined nationality. The breakdowns differ; the total of 329 does not. A second bomb exploded at Narita Airport in Tokyo and killed two baggage handlers, so the Canadian inquiry and the Rae report count 331 deaths in all.

The context was Operation Blue Star. The 2005 report to Canada's Minister of Public Safety by Bob Rae says the June 1984 raid on the Golden Temple and the assassination of Indira Gandhi by her Sikh bodyguards "had dramatically radicalized Sikh activism in India and around the world". The report dates the assassination to November 1984; UPI's report on it is datelined 31 October 1984. The report also finds that the bombing was the result of a conspiracy conceived, planned and executed in Canada. ThePrint reports that the plot is said to have begun after Parmar visited Reyat soon after Blue Star, and that Reyat reportedly cited revenge for Blue Star.

Where: The Atlantic Ocean off Ireland; Narita Airport, Tokyo; and Canada, where the plot was made.

Why it mattered: It remains the deadliest attack in the history of aviation before 11 September 2001, and almost all the dead were civilians. It also became a case study in official failure. The Major commission, appointed in 2006 and reporting in 2010, described a "cascading series of errors". ThePrint lists some: surveillance of Parmar was lifted on 16 June 1985, a test blast was mistaken for a gunshot, and the intelligence service later destroyed its tapes. Reyat walked free on 16 February 2016.