With a significant 'winter storm' expected to blow throughout Ontario this week, Porter Airlines says it will offer complimentary flight changes to those affected.

On Tuesday night, the Toronto-based airline said it would offer these free flight changes to passengers whose flights are impacted by the weather on Thursday, Friday, and Saturday.

Travellers looking to reschedule their flights, however, will be able to move them until Dec. 26, and will have to call Porter’s call centre for assistance.

In an earlier tweet, the airline said it is currently experiencing a “third-party network outage,” impacting its services, including its website.

“At this time, we don’t know when service will be restored,” a spokesperson for the airline confirmed to CTV News Toronto. But those who require assistance at this time can contact the Call Centre at 1-888-619-8622 up until 10:30 p.m. EST.

Some flights at Toronto Pearson International Airport have already been cancelled and delayed, mainly due to the winter weather conditions in Vancouver.

“Passengers are advised to check the weather forecast ahead of their flight and be prepared in case their flight is affected,” Michelle Silva, a spokesperson for the Greater Toronto Airports Authority (GTAA) told CTV News Toronto via email.

On top of the inclement weather, Silva says Pearson is bracing itself for “one of the busiest times of the year” and are expected as many as 130,000 passengers a day this week.

'MAJOR WINTER STORM'

Environment Canada issued special weather statements throughout southern Ontario, including the Greater Toronto Area, with a “major winter storm” expected to start pouring late Thursday.

“Precipitation may begin as rain or snow late Thursday before transitioning to rain in many areas Thursday night,” the statement reads. “Temperatures are expected to plummet on Friday leading to a potential flash freeze for locations that receive rainfall.”

The frigid temperatures and potentially heavy snow will be coupled with strong to potentially damaging winds, the weather agency says.

Blizzard conditions are also possible for areas downwind of Lake Huron and Georgian Bay, starting late Friday and continuing into the weekend.

With files from CTV News Toronto’s John Musselman, and CP24’s Jordan Fleguel