From Stephen Stanley
Watermarked PDF – $5.00 USD
I play World War Two games in 1:100 scale with my models, but use a hex-based system – sort of a huge boardgame.
Hexes have several advantages: they make calculating range and movement much quicker. I admit that setting up your terrain is time-consuming, but the play is simpler.
You're probably familiar already with hexes, and here is a complete system including aircraft and ground combat.