The hangar is where you store and upgrade your active planes. You can decide which machines from your fleet should be present in your hangar. You can freely swap them between selected hangar spots by choosing the plane from the tree and picking the one to be replaced at the bottom of the screen.

The planes occupying your hangar slots are actively used in Battles. Each slot allows you to use an additional plane if your previous one is shot down. You can purchase up to 5 slots in the hangar and so prepare 5 planes to be used in battle. You can decide on the order in which planes will spawn each time an active machine is downed.