Nav Canada said a flight planning computer had crashed, resulting in many delays for departing flights and both cancelled and delayed incoming flights.
Spokesman Ron Singer had said the problem was not affecting the safe operation of the air traffic control system at the airport.
Nav Canada said in its Twitter feed that it was ‘‘working hard to fix the problems‘‘ and were ‘‘safely clearing the backlog.‘‘
By early Friday, only a small number of delays and cancellations were listed on the Pearson Airport web site, and the bulk of those were due to poor weather in Newfoundland and the upper U.S. Midwest.
Nav Canada also said it regretted the inconvenience and disruptions to airlines and passengers caused by the delays.