You should be able to open the controls menu again, and on the aircraft tab, make sure that "Mouse Aim" is selected instead of any of the other simplified/realistic control options. If the button mapping itself is messed up or you have overlapping controls, go to the "full-real controls" section, remove the keybind (Click on the key in the menu, then look to the lower right for the key with an X icon on it). After, go back to the "mouse aim" controls.