Keypad Plus Key zooms in.

You can also opt to increase the "Visual Scale" of the planes as well.

I find this somewhat unrealistic though, and the "Keep ground in view" mode is most representative of what you experience at an airfield.

Planes do get relatively small in your real field of view.

You should also learn how to control the plane, not by seeing it's visible orientation, but rather how it behaves to your control inputs.

This is an important skill to acquire.