Keep Calm and Carry On (Without Carry On)
And Always Pack Clean Underwear!

By Trevor Dunn, Associate Producer, CBC News

For the second day in row Transport Canada has called in the cavalry. The RCMP will be backing up regular security staff at airports in Toronto, Calgary and Edmonton. Local Montreal police will be working Trudeau International.

Anyone who's set foot in an airport since Christmas Day knows why the back-up is needed. In the wake of Umar Farouk Abdulmutallab's attempted bombing of a transatlantic flight headed for Detroit, Transport Canada has tightened security regulations for all U.S.-bound flights. And that's created some major headaches at airport check-ins and security points. Passengers complained of long and chaotic line-ups over the weekend and on Monday.

The heightened regulations include a ban on all carry-on bags, which meant check-in lines at Toronto's Pearson International Airport slowed down as surprised passengers made last-minute luggage adjustments. There are some exceptions for the carry-on ban, like medication and small purses. A full list can be found on Transport Canada's media release.

Also, if you're flying south of the border be prepared for a pat-down before you board. Umar Farouk Abdulmutallab is accused of smuggling chemical explosives aboard the Northwest Airlines jet by hiding them in his pants. Now there are reports the chemicals were actually sewn in his underwear. ABC News has photos of the remains of Abdulmutallab's alterations. The photos show a pair of burnt briefs with a packet of white powder protruding from the crotch.

Transport Canada says the increased security measures will be in place "at least for several days".

There's still no word on how long the RCMP will be providing back up.