Photographer Julian Elnasser spotted the two aircraft over Death Valley earlier this year. The secretive RAT55 NT-43A is thought to be almost exclusively used to test the airborne radar signatures of stealth aircraft.
While this is not the first time the two aircraft types have been spotted or reported operating alongside each other, with much of RAT55’s operations remaining a mystery, any look that we do get of the aircraft in use becomes quite interesting.
RAT55 working with a B2 #rat55 #b2 #ratt55 pic.twitter.com/mezwJKtJd8
— Julian Elnasser (@LAXSPOTTER97) May 28, 2025
Photographer Julian Elnasser described his RAT55 sighting to The Aviationist:
“I was staying in Las Vegas and saw it was out flying from Groom towards the R-2508. So I decided to try my luck and hurry on out to Death Valley near Furnace Creek. Approaching the town I saw the 2 and immediately pulled over, they were pretty low. After the first pass I moved closer to the valley itself and observed 2 more passes before they RTB’d.”
RAT55 – which reportedly stands for Radar Airborne Testbed, with the number being a shortened form of the aircraft’s serial number (73-1155) – operates primarily from Groom Lake, otherwise known as Area 51, though it does make occasional journeys elsewhere. This base would of course be the perfect location for an aircraft involved in the testing and evaluation of stealth aircraft, with direct access to huge swathes of heavily restricted airspace where classified prototypes can be flown away from prying eyes.
World’s Most Secretive 737 “RAT55” Just Made A Rare Public Appearance
The highly modified NT-43A bounces around between secretive test bases and is used to collect radar data on stealthy aircraft in-flight.
Story: https://t.co/KLPzmXhrdG
— Tyler Rogoway (@Aviation_Intel) May 23, 2025
One of the main active programmes that RAT55 is almost certainly involved in is the B-21 Raider, which is designed to be the successor to the B-2 Spirit seen in these images. While the B-2 remains in service, though, continual maintenance routines and upgrade programmes mean the airframes must be routinely trialled and evaluated to ensure they can perform to specification.
While we can’t be sure exactly why this B-2 undertook this specific flight with RAT55, it’s likely that the specific airframe has either recently completed a significant overhaul that may have affected the radar-absorbent skin, or been furnished with new upgrades which now need to be certified as not having a negative impact on the aircraft’s radar cross-section.
Thanks to footage captured from Tikaboo Peak by Roy Jeuring, supplied to Area 51 research website Dreamland Resort, we know that a B-2 Spirit operated over, and apparently even took off from, the secretive base on Apr. 21, 2025. Dreamland Resort founder Joerg Arnu theorised, based on dish antenna activity at the base, that the aircraft was operating with Area 51’s own radar cross-section testing range. This would offer a similar function to RAT55, albeit from the perspective of a static ground radar rather than a moving, airborne one.
Death Valley is one of RAT55’s most common operating areas, though with the range of modern radar systems we don’t really know how far away some of its ‘customer’ aircraft might have been operating during different flights.
RAT55
NT-43A pic.twitter.com/63gbufDxwb
— MilradarJP (@MilradarJP) January 22, 2025
The aircraft was originally delivered in 1974, and is based on the Boeing 737-200. It still features the distinctive low bypass JT8D turbofan engines used by these early model 737s, prior to the introduction of high bypass turbofans on the 737-300. Until the early 2000s, 73-1155 was a regular T-43A used for navigation training.
After its conversion, from 2010 it became the only remaining T-43A in service, gaining an N prefix to become an NT-43A. Under the U.S. military mission design series (MDS) the status prefix ‘N’ denotes a permanently configured test aircraft. It can also be seen used by the NKC-135R Stratotanker test tankers based at Edwards Air Force Base.
For those who follow the world of shadowy U.S. military aircraft, RAT55 has become a legend, and its appearances on flight tracking applications are well followed online.
Many thanks to Julian Elnasser for providing us with these images of his incredible catch. You can find him on Instagram and X/Twitter.
