u/FSM-35-firebion

Before he even fought in the skully ressurection,(that's how i call the war in air combat) he was already a world famous ace, which the air combat intro hinted at us, and since mercenaries often has a bigger pay on their paycheck, he would have been already rich

Adding his victory at stopping rebels at skully islands, it would sure add another huge paycheck on his bank account

And finally, since he once again returned to fight the coup de'etat in ace combat 2 or ace combat AHL, it would sure add another incredibly huge sum in his bank account

Finally, since mercenaries buy their OWN equipment, HE can afford the XFA-27A himself

Complete mission 3B

I mean, if ace combat 8 features the pre-transition from nations to megacorporations and the rise of COFFIN technology, then ace combat 9 should feature the REAL intercorporate war, or the remnants of nations trying to destroy the meaning of a mega corporation