Secretive 737 Radar Jet ‘RAT55’ Has Begun “The Next Phase Of Its Career”

As TWZ has just reported, the U.S. Air Force’s highly secretive NT-43A radar cross-section measurement platform is supporting the launch of NASA’s Artemis II space mission. Now we’ve learned that this reflects the start of an entirely new stage in the career of the notoriously shy aircraft, also commonly referred to by the callsign RAT55.

“After decades of flights supporting the Air Force in various roles, the NT-43A Radar Test Bed is being transitioned to start the next phase of its career,” an Air Force spokesperson has told TWZ. “Beginning with data collection during the upcoming launch of Artemis II, the NT-43A Radar Test Bed will continue its legacy of excellence in supporting some of our nation’s most important and technologically advanced capabilities.”

The video below shows RAT55 making a very rare public appearance at Rick Husband International Airport in Amarillo, Texas, last year.

When asked, the Air Force spokesperson said they could not provide any additional information about how this unique aircraft might be utilized in the future. TWZ has also reached out to NASA to ask whether it has any further plans for this jet.

To be clear, getting a statement about RAT55 like the one above is already highly unusual. The aircraft is often referred to as the most secretive Boeing 737 in the world. It is understood to be based at the Tonopah Test Range Airport (TTR) in Nevada, a remote and highly secure facility long used to conceal shadowy aircraft programs. When the NT-43A has been seen, it has usually been from afar, as it has flown around the U.S. military’s flight testing hubs at Area 51, also in Nevada, and Edwards Air Force Base in neighboring California. The jet has only very rarely appeared anywhere else.

Still, it has become instantly recognizable from its heavily modified nose and huge radome protruding from the rear of the fuselage behind the tail. RAT55 is festooned with other bits and bumps to support its primary mission of signature measurement in support of stealthy aircraft programs. The two huge radar arrays at the front and back of the aircraft allow it to precisely measure the radar signatures of stealthy aircraft flying nearby. This information is used to validate low-observable (stealthy) coatings and other design elements. Electro-optical and infrared sensors are also fitted above the two main radomes. Being able to collect signature data mid-air offers advantages over doing so on the ground, since the subject can be continually observed from all angles, including overhead. You can read more about what is known of the NT-43A’s capabilities and role here.

TWZ has been talking for years about the prospect that RAT55, which is now more than five decades old, could just be getting closer to being retired entirely. The jet is a heavily modified conversion of a T-43A trainer aircraft, which is itself a militarized version of the Boeing 737-200 airliner. The Air Force retired the last of its standard T-43As in 2010. Usage of first-generation 737s in any configuration is dwindling globally, and the remaining examples will only become ever-more challenging to support.

With all this in mind, TWZ has also been watching closely for a replacement for RAT55 to appear. However, to date, no explicit successor to the NT-43A has definitely emerged.

In the meantime, NT-43A could now end up being a key aircraft for support space launches and recoveries. It could also perform other testing and development duties unrelated to space launches and low-observable capabilities. If it becomes available to more customers, its unique services could be in high demand, especially with a new stealth boom on the horizon with new fleets of Collaborative Combat Aircraft drones.

If RAT55 does now come more into the light after decades of largely being a ‘ghost’ within the U.S. military flight test community, we may start to learn more about the aircraft, in general, as well as what the future holds for it and any potential successors.

Contact the author: joe@twz.com