Many of the 16-player SP maps have helicopters, both gunships and transports, however there are only a couple of maps which have fixed-wing aircraft. Operation Clean Sweep is one.

This forum http://dynamic.gamespy.com/~bf42players/ might be of interest to anyone who plays BF2 (or the other games in the BF series) offline or co-op, there are a number of mods in development to expand the SP maps to 32 and 64-player size. Most of them are very rough/unfinished at the minute, but hopefully more polished and playable ones will be released in the future.