The flight started in Toronto at flight 181. Proceeding to its next destination at Montreal, the designator changed to 182. The aircraft was Boeing 727-237B reg: VT-EFO.
The 747 struck the sea roughly 110 miles west of Cork, in Ireland on Sunday, June 23rd 1985 (yes I mean 1985)
The DFDR and DVR were recovered from the 7,000ft. deep water, and indicated that while flying at FL310 at an IAS of 340MPH, all power was lost to the recorders. However, half a second before, a loud noise was heard on the CVR tape which was concluded to be a bomb.
The bomb was placed about Canadian Pacific flight 060 from Vancouver to Toronto. The person who was to carry the bomb on board insisted at Check-in at Vancouver that the bag be transferred to flight 181/2 of Air India when it arrived. The check-in assistant explained that since he had only a stand-by ticket on Air India 181/2, this could not be done. However, he persisted and the lines were long with people; and so she gave in and thru checked the bag to London.
However, the man never boarded the flight in Vancouver.
An hour before Air India 182 dissappeared from radar screens at Shanwick Oceanic Control in Lancashire, UK, a bomb exploded on the airside side of Narita International Airport in Tokyo; the bag should by that point have been on board Air India 301 for Bangkok and Delhi; however, this bag had also been checked at Vancouver, but due to the fact that CP 003 from Vancouver to Narita, was late, the bag was on the ground when it should have been in the air. The scenario was the same with this bag as with the other. The passenger never boarded the Canadian Pacific flight in Vancouver.
Unfortunately, at Toronto, the baggage-screening equipment was down, so 'hand-sniffers' were used. However, ground crew were later found to be employed directly by Air India, but undertrained, and so did not know how to use the sniffers properly.
Several years later, in 1991 I believe, one man was jailed in Canada for the bomb in Narita. Apparently, the attack was in retaliation for the 1984 attack of the Golden Temple by the Indian Army, a Sikh shrine in Punjab, killing hundreds.
In 1992, a 30-year old was arrested in Bombay for the bombing of flight 182.
Hope this helps!