A new Canadian air safety regime that include a 'no-fly' list, which bars persons considered as 'immediate threat' from boarding aircrafts would come into effect from June 18.

The list was conceived to enable airlines to screen out dangerous passengers from boarding flights within Canada [Images] or bound for Canada and head off possible terrorist attacks, Brion Brandt, a Transport Canada official, testified before the Air India Inquiry Commission on Tuesday.

The names in the list are supposed to be shared -- at least initially -- only with commercial airlines that will be responsible for the actual passenger screening.

But Transport officials are open to the possibility of eventually sharing it with foreign governments as well. If Ottawa ever decides to go that route, said Brandt, it would want some assurances about what use foreign authorities plan to make of the list.

"The obligation would be on anyone who's interested in receiving that information to explain why (it's needed)," he told the inquiry headed by former Supreme Court justice John Major.

However, Brandt acknowledged that the list could be passed on by an airline based in its country that happens to operate flights to and from Canada.

"Our relationship there is with the air carrier. Should their national government require that information it is up to them to decide what they want to do with it," said Brandt, who serves as director of security policy for Transport Canada.

Officials declined to say how lengthy the list will be, but it is expected to have fewer than 1,000 names and include both Canadians and foreign nationals. They will be targeted mainly on the basis of confidential information supplied by the RCMP and the Canadian Security Intelligence Service.

People who are denied access to flights can appeal to a planned 'office of reconsideration' within Transport Canada and ultimately to Federal Court.      

Among the criteria for inclusion on the list is current or former membership in a terrorist organisation, past involvement in air security offences or suspicion on 'reasonable grounds' that a person may be a threat in future.      

But those are merely 'guidelines' that are not specifically written into the law. In practice, the federal transport minister will have wide discretion to decide who goes on the list.

David Lyon, a Queen's University expert on surveillance and privacy issues, told the inquiry the proposed criteria, on the face of it, seem reasonable. But he warned there is room for potential problems.

"The list contains persons who, to put it crudely, are too dangerous to fly and too innocent to arrest," said Lyon.

Ottawa has been under pressure to come up with a made-in-Canada roster of names ever since the 9-11 attacks in the United States.