shoot them before they enter the map.
with some luck you can steal the package with a black hat lol.
I've dropped quite a few enemy CP's, but I was under the assumption that the CP still dropped, right underneath the place of the explosion! I could've swore that I took out a CP carrier coming from behind me from our team's spawn one time, and when I took it out, the CP dropped in the middle by the B flag. I seriously doubt the enemy deployed it there, because the carrier was still in motion. I have several "No Tip" anti-scorestreak medals.
I may be wrong though, its been a while since I took out enemy air support. I would say I would try it later, but I don't even have a class with anti-air support at the moment, I'm stuck on the triple kill for the RPG for diamond launchers. Now, THAT"s a pain! working on and off on the task for over six months! LOL. I wish I would've gotten that achievement before they patched it; it worked before to where as long as the last kill was with the RPG it would work, but that is not the case anymore. I don't think I even had the second tier of achievements unlocked for the RPG when they patched it