Building the world
Because this is an infinite-style game, the player will continue to fly through the world as long as possible. That means you will need to continuously create more of the world for them to see – random buildings, items to collect, and so on. It would be impractical to create this all ahead of time both because you don’t know how far the player will go, and because you don’t want the game to be the same every time you play. It would also be inefficient to load a huge game world if the player isn’t going to see most of it.
For that reason, it makes more sense to use a chunking strategy. You’ll randomly generate the world in smaller pieces, or chunks. You can then create these as they’re needed – as the player moves forward. You can also remove them once they’ve been passed when the game doesn’t need to keep track of them anymore.