Originally Posted by
SeattleDavid
I think you are the one in error - if C is available then upgrades will clear immediately (or at least as soon as you call in). If there were just seats available, but the flight was C0, then your argument would be more correct - but even then it is often the case that C is made available 12-48 hours before a flight, before X is made available and before it goes to gate control.
If you are not EXP and flying a popular route then Miles+ copay is probably the only way to snag an upgrade.
A miles+copay upgrade, which the OP is seeking to use, books into C and will clear immediately on the sectors that have C available at the time of the upgrade request. For sectors that do not have C available, the traveler can be placed on a waitlist for C space, and *should* clear automatically, prioritized primarily by status of those on the waitlist, once the space becomes available--this automated process can be buggy, resulting in upgrades not clearing even when the space has become available. C can become available at any time--it is up to RM when to release it.
On the other hand, complimentary (for EXP and PRO) and 500-mile upgrades (for PLT and GLD) clear into R (formerly X) by a separate automated process, again prioritized primarily by status but less buggy than the one for C space. R can become available at any time inside of T-100, and pax are cleared into available R space in accordance to their upgrade windows (i.e. if R becomes available at T-72, only EXPs and PROs can clear into it, while PLTs and GLDs have to wait until T-48 and T-24, respectively).