Systemwide upgrades can be used to confirm an upgrade whenever there’s confirmable upgrade space, so in theory yes. The catch is that American is quite stingy with making upgrade seats available in advance.
然后下面两个舱位可以用于升舱,但是得和客服确认,这个是用于积分升级的 c 舱,而不是现金票的 c 舱。
If you want to use a systemwide upgrade then you should be looking for either the “A” or “C” fare class:
You need the “C” fare class for all other upgrades, including from economy to business class, and from economy to first class on two cabin domestic flights
Note that in reality the inventory actually comes from a subset of those classes. That’s to say that a flight could have the “C” fare class available, but it doesn’t work for upgrades. In other words, you’ll definitely only confirm an upgrade if the above fare classes are available, but even if they’re available, that’s no guarantee.