A "ground stop" at Pearson International Airport that disrupted incoming and outgoing flights for hours has ended, but the major backlog is still causing headaches for travellers.

Approximately 600 flights have been cancelled, according to the Greater Toronto Airports Authority (GTAA) Tuesday afternoon. A spokesman says it’s the most flight cancellations they’ve experienced in one day this winter.

Passengers are urged to check their flight status before heading to the airport.

A cold snap that feels like -40C with wind chill prompted officials to declare the "ground stop" on Tuesday morning, as officials said the extreme cold was freezing some equipment and making it unsafe for employees to work.

"The doors freeze shut and fuelling freezes. It's just harder to get everything done and as a result the processing of the aircraft is taking much longer." Toby Lennox, VP of GTAA stakeholder relations, said Tuesday.

Earlier at Pearson, hundreds of passengers waited hours to board flights leaving at Canada's largest airport. One woman told CTV Toronto her flight scheduled for 8 p.m. Monday night was delayed until midnight. Passengers were finally allowed to board the plane at 1:15 a.m., where they sat for three hours before being kicked off.

Others, whose flights arrived before the ground stop, were forced to spend hours on the tarmac, where a backlog of planes waited for available gates. And when they made it into the airport, many found that their luggage was not being removed from the planes.

"We have been advised that in order to efficiently process incoming aircraft, guests will be offloaded as soon as gates become available, but baggage will have to remain on board some flights until sometime Tuesday," WestJet said in statement.

"WestJet baggage agents are advising guests on a flight-by-flight basis whether or not their baggage will be affected. We apologize to our guests for any inconvenience this will cause, and we will do our best to offload baggage as soon as we can."

Travellers who made it through baggage claim faced another problem. Many of their cars wouldn't start. In a message sent through Twitter, the airport offered a solution: "Call 416-766-3055 for a free boost if you need one and your car is parked in Terminal Parking Garages or other GTAA-owned lots."

Cancelled and delayed flights led to long lines and crowded gates at the airport. Peel Regional Police were called in a few times for crowd control around a baggage carousel, and boarded a plane to deal with an unruly passenger, a spokesperson told CP24.

The weather is also impacting flights out of Billy Bishop Toronto City Airport. Porter Airlines has issued a weather advisory, warning passengers to check the status of their flights before heading to the airport.

An extreme cold weather alert remains in effect for the Greater Toronto Area, and Environment Canada is predicting a lingering wind chill around -37C into Wednesday morning.

What to do if your flight is cancelled

If a flight is cancelled, airlines are supposed to put passengers on the next available flight, "but available means there's no one else sitting in that seat," travel expert Loren Christie told CTV's Canada AM Tuesday morning.

At a time of year when airports are very busy, this may mean waiting days for a flight. "It depends on the frequency of the route you're on. If you've only got one flight a day going to where you're going, chances are very, very slim," Christie said.

Major airlines like Air Canada may try bringing in a larger aircraft, but a larger plane still may not be able to hold all passengers looking to fly to the destination in question.

For the best chance of avoiding a cancelled flight, Christie recommended initially booking the first flight of the day, because often the plane will have landed the night before. He also suggested avoiding connecting flights and lay-overs whenever possible. If you can't avoid a transfer, try to choose a city as far south as possible where snow and freezing rain are less likely to affect travel.

If possible, travel with carry-on luggage only, to save time.

While travel insurance won't change the fact that your flight was delayed or cancelled, it can affect the amount of compensation.

With files from CTV Toronto's Ashley Rowe and Zuraidah Alman