The extreme cold led to long delays at Toronto's Pearson International Airport, where a “ground stop” halted nearly all North American arrivals for several hours in the morning. About 200 flights were cancelled and many departing flights were delayed.

Although the order has been lifted, Tuesday will be a difficult day for travellers heading through Canada's largest airport. Here's what you need to know.

What caused this problem? In general it appears that a backlog processing incoming flights, caused by today's –21 C weather was the culprit. The airport authority issued a Tweet just after 7 a.m. saying the extreme cold is causing "equipment freezing and safety issues for employees."

It appears there were more planes on the ground than there were gates where they could park, creating a large backlog. CBC News gathered reports from passengers who waited on flights sitting on the tarmac for hours after they landed. When passengers finally got inside the airport, there were long waits for luggage to arrive at the carousels.  As a result, the airport issued a ground stop order.

What is a ground stop? Essentially, it means no new flights are permitted to land at Pearson. The order was lifted just after 10:30 a.m. ET.

Where can passengers get information?  WestJet issued a press release  about the delays. You can check your WestJet flight status here.

Air Canada has information about flights delays here and a flight status tool here .

How was the scene at the airport? Not good. CBC Radio's Metro Morning interviewed John McLean, whose Air Canada flight from Sarasota, Fla., landed at 11:30 p.m. on Monday night. He didn't get off the plane until 4 a.m. Tuesday and arrived at the luggage carousel to find "hundreds" of people waiting for their belongings with no staff to provide updates. Also, there was plenty of unclaimed luggage on the floor. "Nobody seemed to know what's happening," he told Metro Morning host Matt Galloway. "What was frustrating was a lack of information," something a lot of passengers are complaining about.

What's the mood of passengers? At best, testy and tired; at worst, outraged. Police were called to the airport to deal with irate passengers. One passenger commented there were more police at the airport than airport staff to help with the delays.