According to the Air Canada cancellation policy. The carrier grants travelers to drop a booked Air ticket to 7 days before the takeoff with including the cancellation refund. What's more, travelers can follow the means beneath to shape scratch-off:

• Visit the official website for cancellation.

• Select the booking that you wish to drop.

• By entering your surname and booking number, you may access your account.

• To cancel your reservation, go to the login page and click the Cancellation option.

• Airlines send an automated confirmation email, canceling the flight ticket and transferring or crediting the returned amount to the account.
  

You must cancel your reservation within 24 hours after making it, according to the official regulations if the statement is true then passengers are eligible for a full refund.

There is a fee for canceling a flight If you cancel after the 24-hour period.