Originally Posted by zorn

If you want to use a certificate you must request the upgrade from Air Canada. You can phone Air Canada reservations to request the upgrade (ignore the warning about a call center fee - it won't apply to upgrade requests).

If your booking class is Y, M, or U, you will be able to request your upgrade as soon as you make your booking. If you booked online you can request an upgrade online via Manage My Bookings. You will also need to be logged in so that the website knows you are a top tier member. You will also need to enter the certificate number if you make this request online. The numbers are all the same of all certificates. These are:

If you are SE or E wanting to use a SSWU on a lower fare class than Y, M, or U, you will have to wait until your upgrade window opens. SE can request the upgrade 7 days before the flight. E can make the request 4 days before.

How do you make the calculation? Suppose your flight leaves on August 11. Four days before is August 7. Seven days before is August 4. You can call at 12:00am. The relevant time zone is the one corresponding to the flight departure. So, if the flight leaves from YYZ, you can call at midnight YYZ-time.