For highest possibel Fighter ability level to fightere class and do not level to Ace or Squadron Leader. Then max vet them and you will have the best possible ability for your pilots. There are hundreds of forum entries on this that explain why this is so I am not going to explain it again here.
As Long as you have classed on time to fighter pilot then parking and leveling them on a BB or anything else will have no detrimental effect on ability. I might add it is a bit more fun to actualy learn how to use the fighter pilots at lower levels so when you do have them leveled you can actually be effective and help your team.
Enjoy the Game.