So what attributes effect Ground Support Fighter performance? Does speed or fuel or armor or size matter at all?
Relevant wiki info
here.Ground support fighters have the same chance to hit as ground units, although they are not affected by any negative environmental modifiers (such as high gravity or extreme temperatures). Each fighter's to hit chance is affected by its own crew grade and morale.
So no other stats of the fighter matter at all for this - although you should note that the size of the fighter pod does matter tremendously.
However, on the defensive side of things:
Ground-based AA Fire
...
The chance to hit is (10% x (Tracking Speed / Aircraft Speed) x (Morale / 100)) / Environment Modifier.
So speed matters tremendously, and I would assume you need 1 kL of fuel just to maintain a speed greater than zero. However, again, putting too much engine mass means bigger fighters with too little payload, so at some point more fighters will be better than faster fighters.
Size does not matter at all aside from giving you more armor (but fewer fighters per ton/BP, so this is of questionable value). Armor does matter:
If a hit is scored, the damage vs the fighter is (Ground Damage Value / 20)^2 rounded down.
So a LAA with racial attack 10 will deal 1 damage per hit, while a MAA at the same tech level will deal 4 damage per hit. The damage profile appears to be the same as a missile, which means MAA will penetrate a single armor layer and deal internal damage. More armor layers may help especially at high tech levels, but I'm not sure that this would be better than using more fighters.
A weird side note here is that LAA is
useless against enemy aircraft if your racial attack tech level is less than 10, which I doubt a lot of people know and has important implications especially for low-tech/conventional games with multiple player races...against NPRs it does not matter anyways as NPRs cannot use fighters.