Hi Jeff.

You need to edit the CS 707-300 aircraft config file so you will no longer be flying an "Experimental".

This is how it is in the default aircraft.cfg file:
[General]
performance=
atc_type=
atc_model=
Category=airplane


This is what you need to change it to:
[General]
performance=See Flight Manual <- I just added that because I wanted to.
atc_type=BOEING
atc_model=B707
Category=airplane

Mark