WestJet systems were back up and running on Saturday night, but not before dozens flights were delayed.
The IT outage started just before 9 a.m. Saturday and delayed 55 flights by anywhere from 15 minutes to an hour.
More than 10 hours later, the airline said operations at its contact centre, check-in kiosks and on its website were back to normal.
WestJet said all affected guests would be put on flights by the end of the day.
It doesn’t expect any flights on Sunday to be affected.