While war planes were used in WWI, it wasn't until WWII where they really came into their own, being a major part of offensives and military strategy. And while Warlord Games has a couple ways for you to bring aircraft to your tabletops in some games like Blood Red Skies, they also have posted some experimental rules for using them in Bolt Action.
From the article:
This set of experimental rules comes from way back in the origins of the designing process for Bolt Action. As with any wargames system things get modified perhaps because of limitations on time, design brief, or we felt they needed more work. Treat these ‘rules’ as entirely optional and an experimental alternative to the main rules for aircraft in Bolt Action & have a little fun.
Essentially these experimental Warplanes rules would replace the Forward Air Observer rules. In terms of army selection, instead of including an Air Observer, each Platoon can include a Warplane chosen from the appropriate list at the end of this article.
Warplanes are rare and expensive units, and remain on the table for a limited amount of time. Because of the scale of our game, we will concern ourselves only with tactical air power: fighters, fighter-bombers and dive bombers, either strafing or attacking ground targets directly. We feel that strategic attack by high altitude level bombers is satisfactorily covered by the rules for artillery barrages.