If you are searching for a field to specialize under the genre of Aeronautical Engineering, then following are the best choices:

• Electronic Systems.
• Aerospace Propulsion.
• Ground Vehicle Systems.
• Aircraft Structures and Materials.
• Structural Analysis.
• Transportation Systems.
• Aerodynamics and Fluid Dynamics.
• Structural Design and Engineering.

For more information regarding Aeronautical Engineering, consider the link below:

https://www.careers360.com/courses/aeronautical-engineering-course

I hope this helps. Wish you a great day!