Air Conflicts: Secret Wars

I did this double boxing against my alt account, but the same would hold true with a boosting partner. I very rarely saw randoms in this game. (as of writing, less than 500 people on TA own this game and it's a cupcake)

Select "Great War". I personally played the capture the flag mode with winning conditions set to "points" which was basically "first to 3 points". Map is entirely choice, but I always played whichever the default was. These planes are painfully slow, so just grind it out as you would with the other capture the flag methods. I believe you can be either side for this achievement, so pick from the two planes with two stars for speed, avoiding the one star speed plane.

An annoying aspect is that you must actually touch or be very close to touching the flag, which is great in an FPS, not so much in a flight game since they're on the ground. If you're just going for the wins, always pick the quickest plane available. Each match takes roughly 5-10 minutes, with you circling back and forth between grabbing the enemy flag and then flying into your flag to score a point. I would get side tracked into getting a couple kills as well, which slowed me down a bit.

At the end of each match, hit "replay match" to avoid going through the lobby/matchmaking setup again. This will greatly speed things up as the match will instantly restart.