Hangars from GTA Online's Smugglers update are now available for purchase in single player. Such hangars allow you to store up to 12 units of air transport (any plane or helicopter taken from the street from of this list will do).
In the hangar, you can also accumulate cargo and sell it. Cargo theft missions are available from the hangar itself. Requires ScriptHookV.Net and Online Interiors to work. Both are included in the archive.
Installation: unzip the contents of the archive into the game folder.