Download 3DRT-Sci-Fi Gunships FREE Unity. 

6 high detailed real-time Sci-Fi Gunships.
All models are ~900-3000 polygons. Extra higher LOD included.
Each model is mapped with 512×512 Diffuse normal and specular map.
Several models share the same texture pattern.

Check out the details from the Unity Asset Store: https://assetstore.unity.com/packages/3d/vehicles/air/3drt-sci-fi-gunships-15631