Giyari
Aye, they take a % of all your taking all the time, whether they're flying with you or not. As for XP, pretty sure they only take XP from kills that they are involved in, AKA, they need to land a shot on that kill. I don't believe they get XP from anywhere else
I have noticed that my fighter pilots seem to level quicker when I order them to attack rather than setting them on defend. But my pilot seems to claim every kill so what do I know.