Pearson International Airport's operations are slowly returning to normal after job action by workers who refuel aircraft forced hundreds of flight cancellations and delays on Friday.

Shabeen Hanifa of the Greater Toronto Airports Authority (GTAA) called Saturday a "recovery day," much like the day after a big snowstorm.

She said there have been no sick calls yet from workers with Consolidated Aviation Fueling Services, which saw less than half of its expected employees show up for morning and early afternoon shifts at Pearson on Friday.

"Operations are running normally this morning," the GTAA said on Twitter.

However, Air Canada is warning there could be more delays or cancellations throughout the day, and advising passengers to check their flight status before heading to the airport.

Almost 200 flights were cancelled at Pearson on Friday after several workers called in sick, joining an unsanctioned job action that has hit Air Canada the hardest. The job action was not sanctioned by their union, the International Association of Machinists and Aerospace Workers.

Union spokesman Bill Trbovich said 30 of 47 workers scheduled for the Friday morning shift called in sick, while others refused to work overtime. About 20 of 56 workers showed up in the afternoon with one shift remaining to provide fuel for the rest of the day's flights, he said.

The workers say they face job losses when a refuelling contract changes hands later this year.

A number of airlines are switching their refuelling business to Aircraft Service International Group (ASIG) in Toronto as of Oct. 1 and have already moved to Swissport in Montreal as of July 1.

With files from The Canadian Press