"Air Canada experienced numerous delays and cancellations over the weekend. While weather, a disruption caused by a fire at our major hub in Toronto, and other factors affected our operation, some impact was the result of a higher-than usual pilot book-offs," airline spokesman Peter Fitzpatrick said Sunday.
"While Air Canada supports the right of its employees to book off when they are unwell or otherwise unfit to work, we cannot condone such activities as part of industrial action to disrupt our operations and we have asked the CIRB to intervene."
The union representing the pilots did not immediately respond to requests for comment.
Air Canada is in the middle of a bitter labour dispute with its pilots that prompted the federal government to step in earlier this month.
In the face of a threatened lockout by pilots and a strike by ground crew, the federal government referred the matter to the Canada Industrial Relations Board and also passed back-to-work legislation last week that referred the disputes to arbitration.
Numerous Air Canada flights were cancelled or delayed in Montreal on Saturday, prompting the airline to say it was facing a number of "operational challenges."
The situation worsened on Sunday when Toronto's Pearson International Airport was forced to close one of its runways after a fire in a maintenance area on the airfield damaged electrical systems required to operate runway lights.
In the morning's low visibility, the runway couldn't be used without sufficient lighting.
The closure of one of the airport's five runways, combined with the heavy fog, caused widespread flight delays and cancellations as the airport's capacity for arrivals and departures was reduced.
The runway was back in service just before 11 a.m. after the fog lifted and congestion at Canada's busiest airport appeared to ease Sunday afternoon.
Flight cancellations at Toronto's Pearson International Airport seemed to dwindle by late afternoon, though the airport's website showed delays stretching well into the evening.
Scott Armstrong, a spokesman for the Greater Toronto Airport Authority, said the ripple effect of the morning delays and cancellations was expected to continue throughout the day.
"What you see is delays in flights, but also you see the airlines make adjustments in their schedules. So they may decide to cancel one flight and consolidate. So instead of two flights going out to Montreal for example, they'll put all the passengers on one flight and send out one full plane."
Armstrong urged all travellers to double-check their flight status before heading to the airport.
The disruptions in Toronto came as thousands of March Break travellers were heading home.
Air Canada, which cancelled a number of flights out of Toronto, said it had to scrap or delay several flights as a result of the "significant reduction" in runway operations Sunday morning.
"Although restrictions have been relaxed, earlier this morning the GTAA was allowing only 12 aircraft movements at the airport versus 50 or more normally," Fitzpatrick said. "As a result we had to cancel and delay a number of flights this morning."
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