WestJet proactively cancelled flights at airports in B.C., Ontario, and Quebec last night ahead of major winter storms. The cancellations add to a series of disruptions that have thrown the holiday travel plans of thousands of Canadians into chaos.

"The prolonged and extreme weather events that continue to impact multiple regions across Canada are unlike anything we’ve experienced," Diederik Pen, WestJet's chief operations officer, said in a statement Thursday.

The decision to cancel 243 more flights was difficult but necessary, Pen said, in order to fly safely with as little disruption as possible when the weather improves.

More than 1,000 flights have been cancelled by Air Canada and WestJet so far this week. The problems started when a major snowfall snarled airport operations in Vancouver, creating a cascading effect across the country.

Things improved a little yesterday at YVR, but 100 out of 660 planned flights were still cancelled. The airport cancelled a significant number of international arrivals, in order to make space to clear the backlog from earlier in the week.

The Greater Toronto Airports Authority, which operates Canada’s largest airport, says it is ready for an influx of holiday travellers, but the extreme weather is throwing a spanner in the works. Much of the country is under winter storm watches and warnings just two days before Christmas.

“Today's travel volumes at Pearson were as expected, and we've planned accordingly throughout the weekend; however, airlines remain affected by the weather over Western Canada and the U.S. and are still working to recover their operations,” the GTAA said in a statement.

“The GTAA understands WestJet's decision to cancel all operations for Ottawa, Montreal, London, Kitchener and Hamilton for December 23, and both inbound and outbound flights to Toronto Pearson on that day. It is critical during the holidays that our partners continue to make every effort to address staffing provisions and crew allocations to deal with ongoing weather disruptions,” the YYZ operator added.

Things will likely get worse before they get better. Frigid cold in British Columbia is expected to improve by Christmas Day, but snow and potential freezing rain was expected last night through Christmas Eve. Meanwhile, Eastern Canada is bracing for a messy combination of rain, snow, flash freezing and strong winds through Saturday and into Christmas Day.