If the download stops please be aware about the free space remaining and try again. Please note that you need 4 GB of free internal space for an installation and smooth running. If you use an Android device do not use the space of a SD-Card!
Otherwise please delete Aerofly FS 2 and restore the app via “AppStore” or “Google Play Store”. After that don´t forget to restore In-App purchases (like California) via “Restore Purchases” in the aerofly app. Please also ensure that you use the same Apple-ID for aerofly and In-App purchases