Castles In The Sky is a set of free wargames rules for flying battleships. The author writes:

In these pages you will find a game that allows you to play out aerial battles between flying battleships fighting in a mythical turn-of-the-century world. The War of the Worlds is over, but the World Wars are just beginning. You will take command of these massive, armored, battleships in the skies around the world! Your commands will lead your forces to glorious victory or disgraceful defeat. The fate of nations depends on you!