New U.S. security measures that came into effect today for all flights bound for the United States have some airlines warning passengers to leave more time to get through screening, although travellers going through Canadian airports may not notice a big difference.

Under the new procedures, travellers to the U.S. could be subject to detailed scrutiny of their electronic devices, and may have to go through interviews conducted by airline employees.

In light of the change, some carriers, including Delta Air Lines and Cathay Pacific Airways, were telling travellers on flights headed for the U.S. to be at the airport at least three hours before their scheduled departure time so they could get through screening.

The U.S. Transportation Security Administration says there are roughly 2,100 flights daily going into the U.S., carrying about 325,000 average daily passengers. The new measures will impact about 280 airports and 180 airlines, a TSA spokesperson said.

Some airlines have been granted delays in the implementation of the new rules. Two South Korean carriers — Korea Air Lines and Asiana Airlines — have been given until next year to comply on condition they put staff at boarding gates to monitor passengers. Royal Jordanian said it would bring in the new measures in mid-January.

The new procedures replace the Trump administration's ban on laptops in the cabins of U.S.-bound flights from eight predominantly Muslim countries, including Saudi Arabia, Turkey, Egypt, Kuwait, Qatar, the United Arab Emirates, Jordan and Morocco. The ban was dropped in July.

For passengers headed to the U.S. from Canadian airports, there might not be big impact from the new measures because several enhanced security measures were introduced in July.

A spokesperson for Calgary-based WestJet said the airline is aware of the new security regulations and is working with the TSA on them.

"At this time, we do not expect there to be any immediate impact to our guests travelling to the U.S.," WestJet's Lauren Stewart told Linda Ward of CBC News in an email.

An Air Canada spokesperson said all of the airline's flights go through pre-clearance facilities and the new measures have been incorporated into the existing steps. He said that once passengers travelling from Canada go through U.S. customs pre-clearance at a Canadian airport, they are considered to be de facto in the U.S., meaning they are regarded the same as a domestic passenger when they land in the U.S.

Air Canada's website says passengers flying to the U.S. should be checked in no less than two hours for their flight time unless they are flying out of Toronto's Pearson International Airport before 10 a.m. ET, in which case the passengers should be at the airport three hours prior to their flight time, the airline says.

A Transport Canada spokesperson said the federal government is aware of the new U.S. screening measures and they will apply to all flights to the U.S. from Canada. The department is encouraging Canadians flying to the U.S. to contact their airline for more information.

"Details regarding specific security measures and where they apply cannot be disclosed for security reasons," Marie-Anyk Côté told CBC News in an email.