Air Canada has confirmed that delayed and cancelled flights over the weekend were caused in part by "higher-than-usual" pilot book-offs.

In a statement to CTV News, Air Canada spokesperson Peter Fitzpatrick said that while weather and a fire at Toronto's Pearson International Airport on Sunday affected operations, "some impact was the result of higher-than usual pilot book-offs.

"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."

He added that "the vast majority of Air Canada employees are hard at work to get (passengers) safely to destination."

CTV News had confirmed Saturday that about a dozen pilots called in sick, citing stress or fatigue as the reason for their absence.

Late Saturday night, CTV's Ottawa Bureau Chief Robert Fife reported that the airline had referred the issue of pilots calling in sick to the Canada Industrial Relations Board, asking for an injunction against its pilots' union.

The delays and cancellations began on Saturday, when Air Canada cancelled 23 flights, mostly out of Montreal, due to pilots calling in sick. That led to dozens of delays for the airline.

Air Canada and other airlines cancelled or delayed flights Sunday after an electrical fire shut down the lights on one of Pearson International Airport's five runways, just as the bulk of March Break travellers began their journey home.

The small fire in an electrical maintenance area on the airfield closed the runway and caused delays Sunday morning as thick fog rolled into the region.

With the lighting system knocked out, the runway couldn't be used due to low visibility.

Air Canada had cancelled at least 35 flights and delayed another 15, according to the GTAA website. Other airlines have cancelled more than 15 flights and delayed nearly 20.

The runway was operational again after the fog lifted late Sunday morning, but it created a ripple effect throughout the day – and across the country.

"Although restrictions have been lifted, earlier this morning the GTAA was allowing only 12 aircraft movements at the airport versus 50 or more normally," Fitzpatrick said in an email to CTV News earlier Sunday.

A number of flights were cancelled or delayed at Vancouver International Airport Sunday, leaving dozens of passengers stranded or unable to make their connecting flights in other cities.

Some passengers in Vancouver told CTV News that a ticket agent was blaming Air Canada's ongoing labour dispute on some of the flight disruptions.

Meanwhile, Pearson airport's website showed flight delays stretching well into Sunday evening.

"What you see is delays in flights, but also you see the airlines make adjustments in their schedules," Scott Armstrong, a spokesperson for the Greater Toronto Airport Authority, told The Canadian Press.

"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."

Passengers frustrated

CTV's Joy Malbon arrived at Pearson at 5 a.m. for a flight Sunday, only to be told fog and work-related issues were causing some of the cancellations and delays.

Staff told customers to use pay phones and call Air Canada instead of getting an agent at a computer to try and rebook people on other flights, Malbon said.

"One man was very upset because he had missed his connection and demanded his money back," Malbon told CTV News Channel by telephone.

Air Canada then set up a counter downstairs in the airport where at least 200 people were waiting in line to have their flights rebooked or to be put on another airline, she said.

The flight problems come just days after the Senate passed back-to-work legislation to prevent work stoppages at Air Canada.