rook

Hi guys, i'm relatively new to this game and there's one problem: When I fly a mission e.g. a BARCAP, it says in the briefing, that I should stay in the target area for a specific time, lets say 30 mins. Sometimes it happens, that i'm out of missiles after just 10 mins. Since it's useless to hang around defenseless, I usually return home early. Now the problem is, that I always get a "mission failed" in the debriefing, because of returning home to early. Anyone knows a solution? greets