More than 200 flights have been cancelled and hundreds of others delayed to and from Toronto's largest airport after staff responsible for refuelling planes suddenly went on strike.

There were chaotic scenes at terminals and boarding counters at Toronto Pearson International Airport, with some of the delays for several hours or more, causing travel misery for many.

"Toronto Pearson International Airport continues to experience operational disruptions due to ongoing issues with the air carrier consortium's fuel service provider," an airport statement said.

Some workers with Consolidated Aviation Fueling of Toronto unexpectedly took the day off in protest at a decision by an airline consortium to cut ties with it.