Snow blankets Fittons Road in Orillia, Ont., during the winter storm that swept across Southern Ontario on Friday. (Submitted by Annabell Ball)A major snowstorm in southern Ontario added to delays and cancellations across the country on Friday, as the country's busiest airport ramped up staffing to handle weather woes and crowds of holiday travellers.

The storm system covered a swath of the province stretching from Windsor east to Kingston, and as far north as Peterborough, bringing snow and gusty winds into the late evening. The Greater Toronto Area was hit with as much as 20 centimetres of snow, while other areas received upwards of 25 centimetres.

The snow was whipped up by 60 km/h winds that reduced visibility on runways and roads alike.

Planes were still coming and going from Toronto's Pearson International Airport throughout the day, but more than 350 of the 1,200 flights scheduled out of the airport were either delayed or cancelled as of Friday evening, the CBC's Christine Birak reported from Pearson.

Many passengers prepared to spend the night sleeping in terminals in hopes of flying out in the morning.

Since the airport is one of the main connector hubs for flights to all points across Canada, delays affect schedules across the country.

Most Ottawa-to-Toronto flights cancelled

Many passengers were stranded at the Ottawa airport Friday, as all flights to Toronto except one were cancelled for the day by 1 p.m., CBC's Jeff Semple reported from the scene.

Some passengers were able to rebook on the one remaining flight, but the rest will have to rebook on flights scheduled for Saturday or Sunday.

Ottawa airport spokeswoman Krista Kealey said some flights to and from other destinations were also delayed or cancelled, partly because the schedule for a single plane may send it through several airports in one day. That means if a flight from Toronto to New York is cancelled, it won't be available to fly out of New York to its next destination, which could be Ottawa or Montreal.

"So it causes a ripple effect and can sometimes take a little bit of time to right itself once the weather … ceases," she said.

Unlike much of Ontario and the northeastern United States, Montreal received just a dusting of snow Friday. However, flight delays in the affected regions meant planes destined for Montreal touched down late or never arrived.

"The storm is surrounding us. The problems we are experiencing here are that the airplanes can't leave their original airports," said Stéphanie Lepage, a spokesperson with the Montreal airport authority.

Phillip Mikolajczyk and his two brothers were supposed to fly to Miami on Continental Airlines to meet their parents and grandmother for a holiday cruise.

"It's very disappointing," he said. "They are saying it's cancelled until the 24th. That's the next flight we could get."

Meanwhile, dozens of flights leaving the Calgary International Airport were delayed, as travellers faced lineups of up to three hours just to check in.

Extra airport staff

Pearson added extra staff and aircraft to cope with expected delays on one of the busiest travel days of the year.

Roughly 100,000 people were expected to pass through Canada's busiest airport on Friday, the last work or school day before the Christmas holiday break for many.

Trish Krale, spokeswoman for the Greater Toronto Airports Authority, said it's an "all-hands-on-deck" situation for staff.

Air Canada and WestJet continued to offer people travelling on Friday the chance to rebook their flights without penalty.

VIA Rail also said it was prepared to add rail cars where possible to meet the increased volume.

Long lineups

Officials advised travellers to check their flight status before heading to the airport and leave lots of extra time to get there.

Airport officials said people have heeded that advice, with long lineups snaking through the airport terminals before the snow started to fall Friday morning.

Claire Langlois and her daughter were headed to warmer weather in the Dominican Republic. The pair said they were nervous because it was their first time flying.

"We're worried if the flight is going to be delayed or cancelled, or if it'll go on or what. But we were here nice and early," Langlois said.

Christine Smith and her friends were worried their afternoon flight to Jamaica would be cancelled.

"I think we'll probably be delayed. I'm just praying it won't be cancelled, but I think we'll be delayed," Smith said.

With files from the Canadian Press