In my medieval-fantasy world, there’s a secret civilization with modern technology. 

A “powerful” dragon accidentally came across them and they became good allies. The dragon was introduced to the concept of aircraft and it wasn’t long until she decided to ride one.
The dragon shrunk into a more humanoid form, with the appropriate limbs and digits. 

The dragon loved to fly in a fighter plane, so much so that she refuses to fly under her own power as much as before.

Why would this be so?