Straight from my head you fly the mission where eisen and maniac is on the run with both catscratch and vagabond on your wing, if you choose to defect both pilots will join you, if you stay with confed, catscratch supports you but vagabond tries to kill you, forcing you to kill him and cutting short on a large piece of the storyline.
And I think that is the only mission where you fly with two wingmen off of the lexington.