How'd you get those stats, Zelda? MW2 wiki?
Either way, I think you're probably right on the probabilities but I've had great luck with my care packages. I've gotten a few UAV's and counter-UAV's but most of my packages have come with Stealth Bombers, Pave Lows, and Attack Helicopters. It's good for me but I rarely use them because I want them to count towards my killstreaks, which they don't.
A1C Peck