. "The Lockheed Martin CATBird is a highly modified Boeing 737-330 designed as an avionics flight testbed aircraft. The name is an adaptive acronym, from Cooperative Avionics Test Bed; coincidentally, CATBIRD is Lockheed's ICAO-designated company callsign. The aircraft was modified in order to provide an economic means of developing and flight testing the avionics suite for the Lockheed Martin F-35 Lightning II."@en . . .