Air India flight 182, a Boeing 747-237B, was filled to capacity (329 passengers and crew aboard) when it suddenly exploded, broke up, and finally disintegrated as it spiraled down from FL310 into the Atlantic Ocean about 110 nautical miles off the Irish coast on June 23, 1985.
Flight 182 was en route from Mirabel Airport in Montreal to Heathrow Airport in London, and had had a mostly uneventful overnight transatlantic flight until it suddenly disappeared from Shannon (Ireland) ATC's radar screen at about ten minutes after 07:00 (GMT). The flight was about midway through the Vancouver-Toronto-Montreal-London-Delhi-Mumbai west-to-east route that had been one of Air India's regular intercontinental routes for about fifteen years.
Everything about the flight was normal except for two factors; one, the 747-237B was carrying a fifth engine, which was unpowered and mounted under the aircraft's left wing (between engine #3 and the fuselage) as it was ferried from Toronto, where it had been damaged in a runway scrape by another plane the prior year, back to India for repairs. The only abnormality this caused was the extra weight, which was compensated for by shifting the center of gravity in the baggage compartment to the right-most side of the aircraft. The other thing that was odd was that there was a Samsonite suitcase aboard, in the cargo hold, which had been loaded onto the aircraft prior to the first leg of its trek, in Vancouver. The suitcase was full of various clothing and also a small, homemade bomb hooked up to a timer. Although security was tight at the time, due to Hindu/Sikh clashes in India and the threat of random terrorism they brought from either side, this suitcase managed to evade security by being stowed by (as most evidence indicates) Vancouver International Airport ground employee Ajaib Singh Bagri, under the guidance of a millionaire countryman of his, Ripudaman Singh Malik, both of whom are Sikhs. By and large, the official opinion of the bombing was that it was retaliation for the Indian Army's storming of the Golden Temple in Amritsar, which left many Sikhs dead. (The Indian Prime Minister at the time, Indira Gandhi, paid for the affront by being assassinated by her own bodyguards, all of whom were Sikhs. Quite a lack of foresight on her part, IMO.)
After the aircraft disintegrated and fell into the sea, most of it sunk to a depth of around 2,000m, making wreckage recovery extremely difficult. Surface vessels from the Irish Navy, the Canadian Coast Guard, and a number of English merchant ships combed the area of Flight 182's last known position for about three weeks, until they finally picked up on an electronic beacon that had been a part of the aircraft, which was meant to operate for 30 days independently if it was separated from the avionics panel. On July 9, 1985, the Canadian Coast Guard submersible John Cabot was dispatched to retrieve the CVR and FDR, which it did without incident. However, since they were officially the property of Air India and thereby the Indian government, a delay of another day ensued while the boxes were flown to Mumbai for examination. The data recorders revealed that they had both stopped working at exactly the same instant, which indicated that the aircraft's power was abruptly cut, meaning the suitcase containing the bomb must have been stowed very close to a generator array in the cargo bay. The loss of power, of course, resulted in an explosive decompression and what essentially amounted to a rapid fall from the sky and subsequent disintegration and sinking. There were no survivors, and the extent of the damage along with the rate at which it fell (at about 0.3g, close to weightlessness) meant that probably everyone on board had died before the impact with the sea. If anyone had survived the explosive decompression, breakup of the aircraft, and the rapid descent, they would've immediately died when they hit the water. The flight crew, however, seems to have died instantly; the last thing recorded by the CVR was a completed repeat of a squawk request from the Air India captain to Shannon ATC. A few seconds after that transmission, the CVR stopped recording and Shannon lost the radar reading on the 747.
As it turned out, another explosion had occured; not on Flight 182, but half-way around the world at Narita International Airport in Tokyo, where a Canadian Pacific Airlines 747 (flight 301) took substantial damage on the ground when a suitcase with a bomb in it exploded. Apparently that one's timer was off, because the plane was empty and parked at the time. The spooky thing was that half an hour before the explosion, the 747 had arrived from Vancouver, and had taken off shortly after Flight 182 did. If Flight 301 had been even a few minutes late, the result would've been much the same as Flight 182's final destiny, only with Flight 301's remains and former occupants sinking into the Pacific Ocean just off the coast of Japan. Instead, it blew up on the ground, and killed two Narita ground employees. An investigation turned up the name "L. Singh," who was booked on separate Canadian Pacific flights bound for both Narita and Bangkok International Airport in Thailand (though there was no incident there). He didn't show up for either flight, but it turned out that the suitcase that exploded at Narita belonged to him. As all male Sikhs bear the name "Singh" (either as one of several middle names, or as a last name), the investigation for "L. Singh" went nowhere fast. Nothing has been discovered about him in the intervening 20 years, and most authorities believe that it was a ruse planted by the aforementioned Ajaib Singh Bagri and Ripudaman Singh Malik and their cohorts.
Bagri was a blue collar industrial worker in Kamloops, and became ordained as a Sikh minister in the early 80s. Malik was an entrepreneur, having owned a number of clothiers in Surrey and Vancouver. Both are naturalised Canadian citizens. The trial for both men began on April 1, 2003, and carried on until March 16, 2005. In 1999, both men were arrested and jailed, where they remained until the trial began. There was, however, a third piece to the puzzle; a naturalised Canadian citizen named Talwinder Singh Parmar. That puzzle piece was missing — he died in India in 1992 during a shootout with the state police force (and was canonized as a martyred saint by the Sikhs immediately after). The Canadian court officially recognized him as the mastermind behind both bombings based on various evidence and witness testimony. Bagri and Malik, however, were both acquitted. Justice Ian Bruce Josephson of the BC Supreme Court found for the defendants, citing a lack of real hard evidence that linked the two to the bombings and of widely conflicting witness testimony. Vancouver has a large Sikh population (in fact, it is the second largest in the world outside of India; the first is London), which made both of the suspects quite (favourably) popular there and in India. Followers of the trial were disgusted with the acquittals, and I can't say I blame them. Rumours of the RCMP and the Crown's incompetence in handling evidence and witnesses have been spreading since 1985, and if they'd conducted a more complete investigation, they probably would've had enough to nail both Malik and Bagri beyond a reasonable doubt. Both of them are unabashedly militant; Bagri has been quoted as saying "Until we kill 50,000 Hindus, we will not rest" at a Sikh rally in New York City shortly after the bombings. That may be merely circumstantial evidence against him, but coming so close after the bombings, how could one be so callous?
The fourth and final member of the anti-Hindu Sikh team is Inderjit Singh Reyat, who admitted in 2003 to building the bomb that brought down Flight 182, and the bomb that killed the Narita workers. He was given a pithy five-year prison sentence for manslaughter. (Manslaughter? For 331 deaths? What a world, what a world...)
According to the RCMP and the Crown, the cost of the case has exceeded $130 million (CAN), but both have vowed to continue their investigation into it, no matter what the additional cost. Given that they have been working on this case for 20 years and had both of their most likely suspects set free, it is very unlikely that the true reason behind both crashes and the deaths of 331 people will ever be discovered.
Sources:
http://www.cbc.ca/story/canada/national/2005/03/16/air-india-advance050316.html
http://aviation-safety.net/database/record.php?id=19850623-2
http://www.airdisaster.com/special/special-ai182.shtml