Here is the full list of all 23 Sky Knights achievements.
Kill 5 players
Kill 4 ground vehicles with a single bomb.
Kill a AAA with guns.
Kill 25 players
Perform 100 player kills.
Perform 500 player kills.
Perform 1000 player kills.
Perform 5000 player kills.
Perform 50 AAA kills.
Perform 250 AAA kills.
Perform 10 FOB kills.
Perform 50 FOB kills.
Perform 100 player kill assists.
Perform 100 perfect landings.
Outmaneuver an enemy, making them crash without shooting them down.
Make 4 air-to-air kills in a very short amount of time.
Make 5 air-to-air kills in a very short amount of time.
Make 5 consecutive player kills without getting killed by another player.
Make 9 consecutive player kills without getting killed by another player.
Make 25 consecutive player kills without getting killed by another player.
Kill a player immediately after performing a loop.
Kill a player with guns while flying inverted.
Kill the developer.