Originally Posted by Daveyb101

I believe the upgrades clear at T-72. My last certificates cleared when I called reservations at T-24. You can call reservations to upgrade as close as T-4. Certificates require availability in A, P or D buckets. To check the availability, do a dummy booking for first class seats, and at the very end of the process (after seat selection (skip it) and where you would enter payment info, there will be a small link at the bottom of the page allowing you to review the fare rules. In the top left corner of the resulting pop-up, it will state the fare class of the ticket(s) you're looking to "purchase". As a practical matter, if there's only one or two seats left, you're probably looking at F class, which will not upgrade. If there are still six seats left and selling for $6-900ish (west coast), there's probably upgrade space.