i've often eyed the various 1:350th scale packs of naval aircraft on amazon, mostly the trumpeter and Tamiya stuff.
this would give F-14 tomcats, F-18 Hornets and super hornets, A-7 Corsairs , F-4 Phantoms, A-6 Intruders, AV-8 Harriers, Seaking helicopters, MV-22 Ospreys, etc..
not to mention Mig-29K's, Su-33's, and various non-US aircraft.
these kits are meant for customizing 1:350th scale model naval vessels, particularly the Aircraft carriers, but they should be close enough to work for battletech. and at around $12 for 6-8 aircraft models, aren't a bad deal. (there are also tank, truck, and humvee packs in the same scale, for those Amphibious assault ship fans, which would make a cheap way to get generic ground vehicles.. $12 for around 16 plastic vehicles on those)