Ace of Aces

There is one ace per campaign segment, so 8 in all. Ish. Make sure you get one in each segment - but if lucky you may get 2 in a segment (I got 2 in the 5th segment). They will be randomly present on the randomly generated missions in each segment. Keep grinding the missions until you get the ace. They will often take two attempts/missions to kill as they will usually escape the first time (assuming you're not hanging about in the mission!). Ofc aces are tough; upgrade stuff before attempting and don't be afraid to run away and try again later if you're getting battered.