NWH Aerodynamics
NWH Aerodynamics is a flight simulation and aerodynamics package for Unity with a focus on realism, ease of use, and flexibility. This asset is a part of NWH Physics World.
Gamico Asset Store offers a collection of Unity assets,previously paid,which are now accessible for free from the Unity assets store.
Silantro Flight Simulator Toolkit that allows you to set up, model and simulate any Fixed-wing aircraft. Details: Silantro Flight System provides AAA flight simulation physics with superb aerodynamics, very realistic.