OTTAWA - Don't expect tighter security at Canadian airports to relax until the United States gets over its latest air scare, aviation experts say.

The ban on certain types of carry-on luggage on U.S.-bound flights, along with other restrictions, are likely to last as long as the Americans want them to.

"Canada is very much a victim of the United States," said David Gillen, director of the University of British Columbia's Centre for Transportation Studies.

"They're the ones who (are) driving the entire process. So all that we can really do is react and try and change the thinking of (U.S.) Homeland Security, that they should be looking for people rather than incidents . . . (that) is, I think, a very difficult process."

Enhanced security measures have been in place since an apparent terror attack was thwarted on Christmas Day.

Umar Farouk Abdulmutallab, a 23-year-old Nigerian man, was arrested after he allegedly tried to bring down the Northwest Airlines flight from Amsterdam to Detroit.

The incident prompted authorities to at least temporarily ban carry-on bags on flights into the U.S., though items such as small purses, coats, laptops and medication or medical devices are allowed.

Transport Canada says the restrictions will continue until further notice.

"Right now, we're evaluating everything and our options," department spokeswoman Melanie Lafrance said Sunday.

"Until further notice, they're in place."

But the Canadian government actually has little say in the matter, says the head of the Air Transport Association of Canada.

"Transport Canada, I don't think has a word to say in it," said John McKenna, the organization's president and chief executive officer.

"They're going to abide by American decisions on this anyway, because otherwise we'll be denied the right to fly over U.S. airspace."

Added Gillen: "I don't think we have a big stick at all."

And he cautioned against expecting a return to normal when airport security concerns abate.

"In the past, what you see is the memory fades, and gradually there is a relaxation going on," said Gillen, who has advised the U.S. Federal Aviation Administration, the U.K. Civil Aviation Authority and Transport Canada.

"But I think that in each instance what happens is you move to another threshold. And even with the relaxation, you don't move down to the previous location that you were.

"In other words, there's always another layer, there's always another issue that's been added on. So it's almost like walking up a set of stairs, where you're cumulatively building all of the restrictions that are put in place."

U.S. President Barack Obama has said there was a systemic failure to prevent the attack and ordered a thorough review of security shortcomings. The president has summoned Homeland Security officials to meet with him Tuesday at the White House.

On Sunday, the president's top counterterrorism adviser cited "lapses" and errors in the sharing of intelligence and clues about the plot.

But John Brennan, who is leading a White House review of the incident, denied U.S. intelligence agencies missed a "smoking gun" that could have tipped them to the terror attempt sooner.

The Associated Press, citing an unnamed senior British official, reported Sunday that British intelligence officials knew Abdulmutallab had ties to U.K. extremists but did not consider him a high enough risk to alert American authorities.