A major snowstorm sweeping through parts of southern and eastern Ontario is putting a wrench in travel plans for many residents hoping to get away for the holidays.

Toronto's Pearson International Airport listed hundreds of flight delays and cancellations as the storm tightened its grip on southern Ontario Friday. At least 300 flights were cancelled and many others were delayed, on what is considered one of the busiest travel days of the holiday season.

The cancellations and delays in Toronto were also felt at Ottawa's Macdonald-Cartier International Airport.

"If an aircraft cannot get from Toronto, to say Ottawa, then it won't be able to leave to go on to its next destination, which could be really anywhere," said Krista Kealey of the Ottawa International Airport Authority.

"Once those kinds of situations happen, it takes a while, even when the weather ends or when the event ends, to get schedules back on track."

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Meanwhile, many travellers at Ottawa's airport were anxious as they waited to find out if they would be able to fly out of the capital.

"It's been delayed, cancelled. Next flight -- delayed, cancelled," said Jose Salamanca, who was scheduled to fly to Mexico.

"I was trying to get to Toronto and then from Toronto, Frankfurt, but the flight got cancelled," added passenger Simon Hecker.

"We've been delayed by an hour-and-a-half, so far. That's all we know right now. We're not flying out until 6:30 p.m., so we got here in plenty of time," Carolyn Kotva told CTV Ottawa Friday afternoon.

Air Canada travellers can re-book flights

Air Canada has issued an advisory notifying travellers who were flying out of Pearson on Friday that they can re-book their flights without paying a penalty.

Air Canada spokesperson Peter Fitzpatrick told The Canadian Press the airline added flights to accommodate the high travel volume during the holidays, and will aim to get delayed passengers to their destinations within 24 hours.

Meanwhile, Via Rail says it will deal with an increase in train travellers by putting every available car on the tracks Friday afternoon for trains heading to Windsor, Ottawa and Montreal.

Collisions close highways

On the roadways, portions of at least two highways were closed as a result of collisions Friday.

One series of collisions closed southbound Highway 400 near Aurora, Ont. on Friday morning, although it re-opened after 2 p.m.

At least five people were sent to hospital with serious injuries following that collision, which occurred at about 11 a.m. when a tractor-trailer unit jackknifed. That led to several other vehicles piling into each other, said OPP Sgt. Dave Woodford.

Fifteen others were injured, with 25 vehicles involved in the chain-reaction event, he said. None of the injuries were life-threatening.

Meanwhile, Ontario provincial police also closed westbound lanes of Highway 401 between County Road 4 and County Road 6 near Napanee, Ont. for about one hour while two tractor trailers were removed from the highway.

Winter storm hits parts of Ontario

Winter storm warnings were issued for areas from Windsor in the west through to Kingston in the east on Thursday. The warnings predicted snow accumulations of up to 30 centimetres in areas that will be affected by lake effect snowsqualls. Toronto is expected to get anywhere from 15 to 20 centimetres of the white stuff.

"Snowfall rates of 2 to 4 cm per hour are expected at times as the heaviest areas of snow move through," read a statement on Environment Canada's website.

The statement also warns of whiteout conditions across the region, as snow gets whipped up by winds that could gust up to 60 kilometres per hour.

"We may have to actually plough and shovel the same snowflakes two or three times because the winds are very strong, with whiteout conditions," Environment Canada senior climatologist Dave Phillips said Friday morning on CTV Newsnet.

Second storm expected this weekend

Holiday travellers who were planning to get away over the weekend may also run into trouble, as a second storm system is expected to hit the region on Sunday.

That storm is expected to dump as much snow across southwestern Ontario as the current blizzard. However, unlike Friday's storm, it will also hit the Ottawa region.

With a report from CTV Ottawa's Norman Fetterley and files from The Canadian Press