It's either you class or no class once you're at fighter/ace, there's really no delay.
It's also a question of how much money/effort you are willing to get the vets. Should you be willing to have around 120 to 160, it's best to class ace. Anything else is fighter.
But then, this application works only if you have also maxmize your crew with experts and vets.
I am trying to find my old graph made 4 years ago, it's somewhere in imageshacl.