Falcon ST, Aviation Defense Service (AVdef). Dassault Falcon (Mystère) 20/200/XX (U-25) , at Nato Tiger meet 2011,Cambrai,France
This designation was given to two Falcon 20s used by the French Air Force as systems training aircraft. The aircraft were equipped with the combat radar and navigation systems of the Mirage IIIE.
Nato Tiger Meet 2011 Photos
Canadian Airline Blog