Check out the Passenger Bill of Rights. Apparently passengers have the right to be rebooked even on major competitor airlines.

https://www.cbc.ca/news/business/travel-plans-dashed-by-air-canada-strike-you-may-have-more-rights-than-you-think-1.7612143

https://rppa-appr.ca/eng/right/flight-delays-and-cancellations