I can add nothing. This is the most secretive plane in the world.
www.dailymail.co.uk
Hat tip the "The Daily Mail" of the UK for this story and photos.

World's most secretive jet spotted over Area 51
The 'world's most secretive plane' was caught soaring through the skies over Area 51, confirming long-held rumors about the craft's operations.
Hat tip the "The Daily Mail" of the UK for this story and photos.
World's most secretive jet spotted over Area 51
The US Air Force's top-secret RAT55 jet was spotted soaring over Area 51 in Nevada, confirming rumors that this enigmatic radar plane operates from the clandestine Groom Lake facility.
Aviation enthusiast Michael Rokita captured the aircraft from a vantage point 26 miles away near Tikaboo Peak, documenting its touch-and-go maneuvers and final landing on runway 32.
Minutes after landing, the RAT55 was linked to Hangar 18, Area 51's largest and most mysterious hangar, as its massive sliding doors were seen open, suggesting the jet had taxied inside.
The RAT55, distinguished by its 'fat nose,' 'hump on the top,' 'hump on the belly,' and 'big protrusion in the back,' is a specialized aircraft designed for in-flight radar cross-section testing.
This capability allows it to evaluate the stealth profiles of other aircraft mid-air, a critical function rumored to have supported the development of the RQ-80 unmanned aerial vehicle (UAV).
Its operations are typically cloaked in secrecy, conducted in restricted airspace like the R-258 range near Edwards Air Force Base, where it often vanishes from flight tracking by switching off its transponder.
Rokita's sighting confirmed that RAT 55 uses the call sign 'Saber 98,' a thrilling breakthrough that ties the jet's covert communications to Area 51's operations, cementing its residence in Hangar 18.
Using a Nikon P1000 camera and a custom binocular-smartphone setup, Rokita overcame technical challenges, including a dying battery and desert heat haze, to deliver this unprecedented evidence.

Aviation enthusiast Michael Rokita captured the aircraft from a vantage point 26 miles away near Tikaboo Peak, documenting its touch-and-go maneuvers and final landing on runway 32
Outfitted with advanced radar systems, RAT55 is believed to operate primarily as a test platform for evaluating the radar signatures of stealth aircraft.
This includes both existing models, like the B-2 Spirit, which undergoes regular testing to ensure its radar cross-section meets expectations, and new prototypes.
With at least two major manned stealth programs currently under development, the Northrop Grumman B-21 Raider and the Boeing F-47, RAT55's specialized capabilities are likely in high demand.
RAT55, short for Radar Airborne Testbed, with '55' taken from its tail number, rarely leaves the skies over the sprawling, isolated test ranges of South-Central California and Southern Nevada, where it quietly carries out its secretive missions.
The jet’s taxiing to Hangar 18 is particularly tantalizing due to its conspiracy lore as the name’s association with alien encounters, secret projects and black-budget aircraft instantly sparks curiosity.
Hangar 18 remained the largest hangar on the base until the mid-2000s, following its construction in the 1980s.
Its towering height and massive doors could accommodate virtually any aircraft in the US inventory, making it ideal for testing, storage or perhaps even simultaneous classified projects.
Some enthusiasts have speculated that the hangar may house a “museum” of retired or experimental aircraft, hidden from public view.

Minutes after landing, the RAT55 was linked to Hangar 18, Area 51's largest and most mysterious hangar, as its massive sliding doors were seen open, suggesting the jet had taxied inside

The RAT55, distinguished by its 'fat nose,' 'hump on the top,' 'hump on the belly,' and 'big protrusion in the back,' is a specialized aircraft designed for in-flight radar cross-section testing

It was also last spotted in May, flying alongside a B-2 Spirit over Death Valley
Flight paths of Air Force planes that made trips to Area 51
The combination of the legendary Hangar 18 name and its location at Area 51 has cemented its almost mythical status, feeding decades of rumors that have fueled conspiracy theories, from alien technology to top-secret aerospace programs.
RAT55’s recent appearance there only adds fuel to the speculation, suggesting that whatever goes on inside may be as secretive and extraordinary as the legends imply.
It was also last spotted in May, flying alongside a B-2 Spirit over Death Valley.
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 two and immediately pulled over; they were pretty low.
'After the first pass, I moved closer to the valley itself and observed two more passes before they [returned to base].'