A consumer advocate group says it has received about 50 complaints a day about Air Canada since Christmas Eve, when bad weather triggered days of flight delays and cancellations across the country.

Customers wait in line at Vancouver International Airport on Tuesday. (CBC)

Delays and cancellations have plagued Canadian airports for days as airlines struggle to contend with a backlog of thousands of holiday travellers.

Air Canada, the country's biggest airline, had to reschedule a number of flights over the holidays, including all short and medium-haul flights to and from Vancouver on Christmas Eve.

While poor weather was to blame for most of the flight problems, Consumers' Association of Canada president Bruce Cran said most of the complaints are about Air Canada's response to the situation.

"I don't hear anyone complaining about the weather, it's the treatment that they were given, or the lack of decent treatment by the airline in question," Cran said.

Three-quarters of the calls his organization has received in recent days have been to complain about Air Canada. He said the others have mostly offered praise for the carrier's rival, WestJet.

Cran said one of the worst stories has been about an Air Canada flight that spent 12 hours on the tarmac at Vancouver International Airport with its passengers trapped inside throughout the delay.

Some passengers have said they felt like "hostages" because they were told they had to stay on the plane.

"Keeping people prisoner on an airplane for 12 hours on the tarmac is absolutely outrageous, I don't know how [Air Canada] think they had the right to do that," Cran said.

Air Canada has said that a combination of factors, including weather, fuel and crew issues, contributed to the delay and that allowing passengers to wait inside the plane where they had access to food and entertainment was a better option than sitting inside the terminal.

The airline has offered passengers on the flight a $500 voucher.

On Saturday, the Greater Toronto Airport Authority was reporting a number of flight delays and cancellations at Pearson International Airport.

More than 200 flights were delayed and 44 cancelled at the country's busiest airport, largely due to thick fog that hung over Toronto for most of the day because of rising temperatures.

There were also reports of dozens of delays at Vancouver International Airport.

A spokeswoman there said the problem was an issue with airlines, not airport operations, but didn't provide details.

With files from the Canadian Press