perhaps drones could be an enemy/obstacle.
granted that may add the requirement for a story, but IF needed, some dystopian future where some package company has taken over, you are a resistant pilot or maybe just some small startup.
maybe if you continue your build yo can have different iterations.
deliver power machine piece to country/town makes it so it will now light up.
different weather things can add the need for certain paths.
though if you're just going for an open world sort of flying fun game then none of that backstory is required. either way its an awesome game