Justice John Major, heading the Air India Flight 182 inquiry, has asked Air Canada to appear before court and warned that unless the airline relents and attends voluntarily, he will consider issuing a subpoena to compel it to send people to testify.

"The Canadian airline is one of oldest and largest in the world, and it is Air Canada's duty to co-operate with the inquiry," Justice Major said on Wednesday.

Air Canada notified commission counsel earlier this week that it would not be able to attend, but Major says that response was not good enough.

Major's inquiry is investigating the 1985 terrorist bombing of Air India Flight 182 that claimed 329 lives. A key issue is whether domestic and international security rules have been reformed sufficiently since then to ensure another such tragedy never occurs.

The Air India bombing was the crescendo in an international campaign by Sikh extremists that included nine earlier hijackings.

"Air India was the 10th and the big-bang event as far as the Khalistan militant movement was concerned and therefore to that degree it was predictable," University of Manitoba professor Peter St John testified, adding, "We could anticipate that something might happen."

St John began studying aviation security and terrorism after losing his student and teaching assistant, 23-year-old Rahul Aggarwal, in the bombing.

St John's research showed him that for year before the Air India blast, there were cycles in terms of hijackings and sabotage of aircraft that should have been an indicator to aviation authorities.

"You could see the movement gathering for something extreme," St John said, adding, "I don't think that Canadian airport security or Transport Canada or any of our security people were ready for Air India."

St John, who has authored several books on aviation security, was part of a panel of three experts who testified at the inquiry as it began Tuesday to examine the area of airport security.

Rodney Wallis, an international civil aviation security consultant, explained that he predicted a bombing like that of Air India at a US conference in April 1985 and made recommendations that could have prevented the attack.

"What I tried to do is warn that this is the danger -- we had to consider how we cope with this," he said, adding, "We pushed for passenger and baggage reconciliation."

Major asked the experts to predict what could be the next wave of terrorist tactics now that airports are more secure because of the Sept. 11, 2001 US attacks. St John said he thinks planes will always be terrorist targets because of the sensational nature of such attacks.

"Aircraft are so symbolic; they are so powerful in the public mind. You almost have to attack through aircraft to advance your terrorist notions today," he added.