<font face="Verdana, Arial, Helvetica" size="2">Originally posted by bp888:
I've seen this term used in conjunction with using VIPOWs for international upgrade. My understanding is that it means there are only limited number of seats available to use the VIPOW upgrade certificate on. Conversely, I would take it that if an upgrade award is NOT capacity controlled, you can use your upgrade provided there is a seat available. </font>
"Capacity Controlled" means you have to book your ticket in a special inventory (A or C for upgrades, Z or U or T for freebies) set aside flight by flight, and potentially updated/resized hour by hour by the computer revenue whizzes.
If the class you need is available at booking time, it's yours. Otherwise you have to wait and see if more seats are released into that class.
AAnytime freebies (and domestic zone VIPOW upgrades) fall into the regular F/J/Y booking codes, which are the same as full fare revenue tickets and hence always available until the flight is completely booked.