I know i am gonna get flamed for this...
Supplies, the fields have ammo bunkers & fuel tanks, they refill at a given rate so... a base that is experiencing heavy traffic would need a resuply (lancaster with cargo instead of bombs???) gvs & boats would be too slow i think.
Just a thought to eliminate the quake HTC can figure the details. It might even promote that gawd awful thing called TEAM WORK that is what this game is about?