From in the main "Free Flight" window, where it asks you what plane, location, weather, time, etc.  There is a row of buttons, one is marked "Load"  from within here, you get a list of all saved flights, highlight them and then click the delete button for each... once this is done, shut down and restart FSX and it will restart with the default flight which has the ultralight and such... from here, if you load 757 and cycle thru all displays before turning on anything in the plane, I would hope the radar issue you have goes away. :D