http://www.youplay.it/play/bm_GameMove.asp?GameID=646425Happens often enough. In this game, two Allied planes left without honor causing the Germans to score a Tactical victory. If the Allied pilots had stuck around and survived, it would have been a Tactical victory for the Allied side instead!
In League play, the scoring system takes this into account and punishes dishonorable exits. The side exits may turn a Draw into a victory for the opponents, whether from the points (Marginal) or the fact the plane is counted as a kill (Tactical and Strategic).
The nice thing about the Leagues, though, is that a lousy wingman who tends to turn tail will tend to balance things out by screwing over your opponents when s/he flies for them.