Canadian families of the victims of the Air India jet bombing in 1985 have called for a public inquiry following the acquittal of the two main suspects.
Most of the relatives described the verdict as a "travesty of justice"
The authorities "owe it to the 329 victims of this crime," said Eddie Madon, after the judge in Vancouver found two Canadian Sikhs not guilty.
The trial has cost least $100m, and has been one of the most complex cases in Canadian history.
Deputy Prime Minister Anne McLellan said there was no point in an inquiry.
"There will be, tragically, some questions that may very well not be answered," she said.
She likened the incident to the 11 September 2001 attacks on the US, where there were also questions "that will never be answered, as hard as we look".
Flight 182 blew up over the Atlantic Ocean off the Irish coast while it was travelling from Canada to India.
The judge said the prosecution, which alleged the men were seeking to punish India for a crackdown on Sikhs, had failed to prove its case.
There were credibility issues with the witnesses testifying against both men.
Vancouver businessman Ripudaman Singh Malik, 58, and 55-year-old Ajaib Singh Bagri, a sawmill worker, were arrested in 2000 and charged with a list of offences including murder.
The men, who were both born in India, denied any involvement in the crime.
Ripudaman Singh Malik and Ajaib Singh Bagri were arrested in 2000
"I want to repeat publicly today what I have told the authorities numerous times since 1985, that I had absolutely no involvement in any of these criminal activities," Mr Bagri said in a statement after the verdict.
The victims' relatives in Canada and India were unanimous in condemning the verdict.
They said the verdict was a second tragedy - after the death of their loved ones - and asked the Canadian government to challenge the court ruling.
"I cant believe it. I cant believe it," one man moaned loudly in the courtroom.
"Today 20 years on we have lost our families all over again," said Sanjay Lazar, who had travelled to Vancouver from Mumbai to hear the verdict.
"Today's verdict flies in the face of what we believe Canada to be, a fair society," said Lata Pada, whose husband and two daughters died aboard the plane.
Prosecutors had taken 13 months to present evidence, after a 15-year investigation.
Some evidence was lost or destroyed, and two potential witnesses were murdered.
The prosecution had accused the men of helping to plant the bomb on the Air India jet in revenge for the Indian army's 1984 storming of the Golden Temple in Amritsar, Sikhism's holiest shrine.
A second bomb, in luggage to be loaded on to another Air India flight, exploded on the same day at Tokyo's Narita airport, killing two baggage handlers.