The carrier detailed the resumption of its international schedule this summer, which includes 17 routes and 11 destinations across the world from its hubs.
The Montreal to London route will start from 3 August. Capacity on the Vancouver to London service, which has already started, will be increased next month.
Three flights a week from Toronto to Dublin will resume from August 1.
Mark Galardo, senior vice president of network planning and revenue management for Air Canada, said the airline is "committed" to rebuilding its international network.