The federal government has ordered Transport Canada and the Canadian Air Transport Security Authority to tighten security the day after an attempted terrorist attack on a Detroit-bound Northwest Airlines flight from Amsterdam.

Air Canada and WestJet are instructing passengers to arrive as much as three hours early at airports to allow for extra security checks.

Passengers and their luggage will be fully searched at airport screening points as usual, but their bags will also be searched by hand at the gate. Every passenger to the U.S. will also receive a physical pat-down, WestJet wrote in a statement.

Transport Canada has limited passengers to one piece of carry-on luggage instead of the usual two on flights into the U.S.

In addition to the pre-flight security measures mandated by the Canadian government, there are new in-flight rules imposed by the U.S. Transportation Security Administration to limit on-board activities by passengers and crew in U.S. airspace.

Air Canada said in a statement that during the final hour of flight passengers must remain seated. They won't be allowed access to carry-on baggage or to have any items on their laps.

Air Canada suggests passengers avoid bringing any carry-on baggage, and only bring on small items such as a purse, laptop bag, briefcase or diaper bag. It says it will waive any extra fees for passengers who must check extra bags due to the new restriction.

"As a result of the added security precautions, passengers should also expect delayed and cancelled flights as well as missed connections," Air Canada wrote in a news release.

Passengers who miss their connections will not be charged to rebook.

Air Canada warned that although these measures only apply to flights into the U.S., domestic and international flights will also be delayed due to airport congestion.

WestJet says these heightened security measures will be in place until Dec. 30, and Air Canada did not specify a date.

The changes follow the arrest Friday of a Nigerian national who allegedly tried to detonate an explosive aboard the Detroit-bound flight. Passengers thwarted the suspect and the plane landed safely.

Announcements were made Saturday over the loudspeaker at Pearson International Airport in Toronto to let passengers know about the expected delays due to heightened security.

The Nicholas family,  heading to Ft. Lauderdale, Florida to catch a Caribbean cruise, came to the airport four hours ahead of their departure, just in case.

"I'm glad there's heightened security," Cindy Nicholas told CTV Toronto.

The changes follow the arrest Friday of Umar Farouk Abdulmutallab, 23, a Nigerian national who has been charged with trying to detonate an explosive aboard the Detroit-bound flight. Passengers thwarted the suspect and the plane landed safely.

The suspect is currently in hospital in Ann Arbor, Michigan, being treated for burns.

Expect longer lines

Douglas Laird, the former security director at Northwest Airlines, told CTV News Channel that passengers can expect longer lines than usual and that they should remember the restrictions on bringing liquids onto the plane. Passengers are only allowed to bring liquids in 100 ml bottles or smaller, and can only bring one Ziploc bag with liquids on board.

He said the problem isn't that people try to get around the restrictions, but that people who don't fly frequently may be unaware of them.

"The slowdown is people that don't travel, of course they come with containers that are too large, and they don't have the clear plastic bags," he said.

Some airports, such as Chicago's Midway International Airport, have separate security lineups for people who fly frequently and know the rules, in order to expedite their security checks for everyone. But all passengers should expect delays at airports that don't have this system.

Public Safety Minister Peter Van Loan said he spoke with U.S. Homeland Security Deputy Secretary Jane Lute regarding the incident.

"Security threats to the United States are security threats to Canada. The Canadian government remains fully engaged with the Obama administration on efforts to combat terrorist threats," he wrote in a statement.

'Pat-downs' not enough

Larry Johnson, CEO of Berg Associates, a security firm in Washington said that there is no real way to make sure passengers do not bring bombs onto planes until better technology is developed.

Until that happens pat-downs are not enough to fully protect passengers.

"Pat-downs are better than nothing, but not a terribly useful or effective approach," he told CTV News Channel.

Former CSIS senior intelligence officer Michel Juneau-Katsuya told CTV News Channel that it is hard to strike a balance between keeping travellers safe, but also letting them keep them move freely around the airports.

"The challenge since 9/11 is that we want more security, but we don't want to turn it into a police state where everyone is getting a body search instead of getting on the plane," he said.