Flight schedules returned to normal at Pearson International Airport early Friday morning after a computer outage led to significant delays for passengers.

Nav Canada spokesman Ron Singer said the problem cleared up at about 3 a.m. and no delays were reported, as of 5:30 a.m.

Singer told CP24 that technicians are not sure what caused the problem, but they are looking into the matter to make sure it never happens again.

The computer problem involved a flight planning system, causing a traffic jam for departing and incoming flights at Canada’s largest and busiest airport. As a result, many flights were delayed or cancelled.

During the computer crash, flight information for departures was being processed manually, and safety was not compromised, Nav Canada said.

"Air traffic controllers can see the aircraft and talk to pilots in their airspace," Singer told The Canadian Press. "The measures we have put in place to manage a safe and orderly flow of traffic, at a slower pace, are intended to ensure safety."

During the delay, several passengers complained about being stuck on flights as they waited to depart.

In a tweet, one passenger complained that her planed had been sitting on the tarmac for three hours.

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