All flights are now available for purchase via the Air Canada app, at aircanada.com and through travel agents.
The airline tweeted that it was "experiencing an interruption" at its contact centres and website and is working to restore service as soon as possible.
A system-wide computer outage is leading to long lines at airports across Canada on Monday, as some flights are having to be checked in manually.
The company apologized for the inconvenience and thanked customers for their patience.
Winnipeg Airports Authority said flights have been affected so far at Winnipeg James Armstrong Richardson International Airport on Monday. The flight was scheduled to depart at 10 a.m. A similar message was posted on the carrier's official Facebook page an hour later.
At around 11:15 a.m., Victoria Airport reported that Air Canada self-serve check-in kiosks were once again operational.
The new Calgary to Palm Springs, and Edmonton to Las Vegas flights will be onboard Air Canada A320 and Air Canada Rouge A319 aircraft respectively, both offering premium and economy cabins.