Naval Test Pilot School X-26 Program, were modified to QT-2 configuration (QT for Quiet Thruster) by the Lockheed Missiles & Space Company and civil registered as N2471W and N2472W.

In 1967 the aircraft were modified by adding a Continental O-200 engine, V-Belt RPM reduction system, four-bladed Fahlin fixed pitch wooden propeller, and associated airframe upgrades.

They were successfully evaluated in Southeast Asia under the Prize Crew OpEval program for covert ("stealthy") tactical airborne observation in the spring of 1968 (during Têt).

The second X-26B aircraft known as QT-2 N2472W and QT-2PC #2 was restored to SGS 2-32 configuration and has been operated for many years (and known as "72 Whiskey") for paid scenic rides at Mile High Gliding in Boulder, Colorado.

They were later used by the Louisiana Dept of Wildlife & Fisheries (LDWF) and the Federal Bureau of Investigation (FBI) in law enforcement, and by NASA for scientific applications.

Related lists This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.