Tumbling Dice do an excellent range in 1/600. Skytrex also do a few, as do Stronghold (the old SDD range, including a very nice Condor).
In 1/700 you can pick up sets of plastic US and Japanese aircraft for use with the Tamiya / Fujimi / Aoshima WW2 model ranges, and Skywave / Pitroad do useful sets as well (ncluding Luftwaffe types and land based aircraft).