There is a special key. I think it is the "L" key but I don't remember. When the unit blinks, hit the "airdrop" key, you will see a little parachute icon. Place the parachute icon where you want to airdrop and click. The unit will airdrop to that location. If you see an "X" on the parachute it means you are not allowed to airdrop on that particular tile. You can airdrop directly in enemy bases if they are empty and if they do not have the aerocenter complex.
No permanent enemies, no permanent friends.