The European Participating Forces countries Belgium, Denmark, Netherlands and Norway joined (with the USA overlooking it) in a F-16 Mid-Life Update program. Each EPAF country had one Lead The Fleet F-16 at the Lockheed-Martin plant, Fort Worth (TX) which acted as a trial aircraft for the program. For Belgium it was FB21. This FA93 was the Belgian Test, Verification and Installation a/c, stripped to the airframe and re-assembled in a later stadium in order to perform all kinds of work. The MLU is easy to recognize, as the modified F-16s have four antenna arrays just in front of the canopy.

Prototype MLU conversion, still without the "bird slicers" just ahead of the cockpit