The setting you want is in i_server. I know this because I've done exactly the same thing.
It makes perfect sense too, the airdrop arrives MUCH quicker and is less likely to get shot down by OPFOR. It looks so cool seeing that bird fly over and drop the cargo... sometimes, it drops the cargo, then flies around and makes a second pass, as if checking it's dropped it in the right place. Other times, if flies over once, then drops it on the second pass, as if the pilot is checking his dropzone. So cool!
Code:
// Type of aircraft, that will air drop stuff
x_drop_aircraft =
#ifdef __OWN_SIDE_GUER__
"MH60S";
#endif
#ifdef __OWN_SIDE_WEST__
if (__ACEVer) then {"MH60S"} else {"C130J"};
#endif
#ifdef __OWN_SIDE_EAST__
if (__ACEVer) then {
"Mi17_rockets_RU"
} else {
"Mi17_rockets_RU"
};
#endif
#ifdef __TT__
"MH60S";
#endif