Board Thread:General Discussion/@comment-139.0.72.103-20150130150846/@comment-1824272-20150206051812

DRosencraft is correct. Take the dialogue of Rendezvous:
 * Chopper: << Hey, Kid! >>
 * Grimm: << You really should start calling him Captain. >>
 * Chopper: << Forget it. If he's a Captain, then I want him to start trash-talking like a Captain. Man... I'm missing that voice real bad now. >>
 * Grimm: << He's gotten us out of battle for the second time now. As far as I'm concerned, he's our Captain now. >>

The term "Captain" is used as both a military rank and for the position of squadron leader. The members of Wardog weren't actually ranked as Captains until the events of Ice Cage and White Noise, when they got promoted. So the case of "Captain" being used in ACX is likely the same as here, where it was for the position as squad leader and not actual military designation.