Originally Posted by
DLdweeb
To me a battlefield upgrade occurs after you board and are pulled up to FC by the GA or FA. This usually means you were at the top of the list with zero seats available when you boarded.
A gate upgrade, as the name implies, means you are cleared into FC by the GA before boarding, usually 30-40 minutes before departure.
I think most of us use the term "battlefield upgrade" to mean an upgrade at the gate, not an upgrade after boarding.