This "losing the ground" problem is easily fixed by clicking "view" then "ground". If you have more than one view window open, make sure you click somewhere in the main window before you do this.

This will keep the plane and the ground in view all the time. It really should be this way by default, but it is an easy setting to change (you will have to redo this every time you change planes or airports)

This is by far the biggest complaint about RealFlight I hear, and it is so easy to fix it's unbelievable. It makes the sim much more realistic.