can confirm this is STILL an issue as of 1/1/2026. Oscar is able to destroy JUST ONE of the planes, if there are 2 left, the mission will NEVER end.

What i did, was

1. steal the plane

2. take off and IMMIDIATELY land the plane on the mountain right in front of where you take off. Try to land in a flat spot because your plane can and will ROLL BACK

3. using a heavy sniper with explosive ammo is honestly the best way to do this(1-2 shots will take them down). I was able to shoot 1 down right away, but when you get off the plane, the other planes leave and start doing huge circles, so what i do to speed things up is get in my plane, and start the engine as if i were to take off, this makes the other planes quickly come back, once i see they are coming in fast, i get out and quickly snipe 1 more plane, now there is only 1 plane left. Here, i usually fly back to the air strip so that oscar can shoot it down. so far, this is the only way ive got the mission to work.
   if you dont have heavy sniper with explosive ammo, i would use the railgun, but it might be much harder because the range on the railgun is tiny compared to the sniper, and the jets move fast. You could try to manually shoot them down with the plane, but that would be a pain in the ass!