This is a paid asset, but now you can download Spaceship Flight Mechanics for FREE, Please keep in mind this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Spaceship Flight Mechanics v1.0
Spaceship Flight Mechanics provides a well thought out implementation of arcade style spaceship controls and flight mechanics, using both mouse and keyboard-only flight modes for rigidbody ships. These flight mechanics are alike those found in legendary proven space simulators such as Freelancer and the X series.
The framework gives you a very solid and well tested base for building your space game which uses a well thought out scripting system with modular ship components.