I'm wondering why it's so lowpol and triangulated. Game?
If it's for a game...is it a flight shooter? Add guns. Lots.
IMO the buildings need a ton more detail.
You could make a super high pol model of the sparrow (or buildings too) and then bake a normal map and keep the lowpol model for rendering purposes...maybe add twice the detail into the render version.
Normal maps are very useful to use even in rendering if you need to shave off render time.