More than a quarter of Air Canada flights suffered delays on Friday as the airline worked to restore service to normal following a technical issue the day before.

Air Canada had warned travelers early Friday morning that they should prepare for further flight disruptions. In its daily travel outlook, the carrier said that while its computer system is now stable, flights could be affected at nine of Canada’s busiest airports, including Toronto Pearson International Airport, Montreal International Airport -Trudeau and Vancouver and Calgary airports.

Thursday’s outage caused more than 500 flights to be delayed or canceled, more than three-quarters of its trips that day, creating what the company called a “spillover effect” that could lead to further delays Friday.

As of 4:30 p.m. Friday, a total of 144 Air Canada flights, or 27% of the airline’s scheduled flights, had been delayed, while another 33 had been canceled, according to tracking service FlightAware.com.

As many as 56 other Air Canada Rouge flights were delayed, a third of its scheduled flights, and 23 were canceled.

“Air Canada has stabilized its communication system and it is functioning normally. However, due to the effects of Thursday’s computer issues on our schedule, some flights may be delayed this morning as we reposition aircraft and crew,” the airline said in an emailed statement.

“Customers are advised to check their flight status before going to the airport. Our flexible travel policy remains in effect so customers can change their travel plans free of charge. »

The airline did not say when it expected its flight schedule to fully return to normal.

The source of the disruption was in the system the airline uses to communicate with planes and monitor their performance, which Air Canada is in the process of upgrading. On May 25, she was forced to ground her planes for about an hour when the system experienced a separate problem.

That day, 241 Air Canada flights — 46% of its scheduled trips — were delayed, according to FlightAware. Nineteen other flights were also canceled.