This is very easy to do once you have completed Nick Rye's companion mission. Simply get in Carmina, drive it forward 30 feet or so and turn it around. Summon a plane from the hangar. The cheapest one to unlock is $2,500 if I remember correctly. Get in the Carmina and shoot the other plane until it blows up. Repeat nine more times. Only takes a couple minutes and is way less time consuming than finding and dogfighting cultist planes, which is a pain.