I probably have been deleting aircraft the wrong way. I did not think of a right click in the aircraft select list.  I chose to use the Windows Explorer.  I have RF G5.5 and it put a directory Realflight G5 in your My Documents. Click on the directory, then Vehicles and you will find a "Custom Models" directory  and look for the name of the plane you want to delete.  I have done this to get rid of unwanted planes.

When I restart it is gone!   

There may be better ways put it works for so I do it that way.

RT