If you wanted to put every single aircraft on stands, G40 has 50 bombers, 66 tactical bombers and 88 fighters.
That’s a lot of stands and you probably don’t need to do every single one (I personally feel if you add a magnet to each aircraft piece and have enough stands for most situations, you’re set).
I haven’t figured out an exact count yet, so someone else might be able to chime in with a better idea but I would think 20-30 bombers (35mm) and 50-60 fighter/tac stands (25mm) would be a great setup (though probably excessive in most cases).