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; 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.

[1] CATBird has a distinctive appearance, with an F-35's nose and a pair of small canards located just aft of the forward entrance doors.

[2] The aircraft was modified under contract by BAE Systems Inc. at their facility at the Mojave Spaceport.