Tom Clancy's H.A.W.X. 2

This will probably come when you aim to master 15 planes, or if you play a lot of mission replays, or if you play the online a lot, as pretty much every action in the game will net you XP one way or another. Either way you will need to amass a total of around 173,000 XP to get to Level 50. If this is an outstanding trophy for you, then a really easy way to rake in around 1000-2000 XP per 2 minutes is listed in the trophy description for Hard Work Pays Off; it is a method involving farming XP on Mission 19, 'Stand-off'. See this for more help.