The B-21 Raider -- which is not set to fly until 2023 -- is the first new American bomber aircraft in more than 30 years.
America's newest nuclear-capable stealth bomber made its debut after years of secret development and as part of the Pentagon's answer to rising concerns over a future conflict with China.
The B-21 Raider is the first new American bomber aircraft in more than 30 years. Almost every aspect of the program is classified.
The public got its first glimpse of the Raider in a tightly controlled ceremony at the US Air Force's Plant 42 in Palmdale, California on Friday.
It started with a flyover of the three bombers still in service: the B-52 Stratofortress, the B-1 Lancer and the B-2 Spirit. Then the hangar doors slowly opened, and the B-21 was towed partially out of the building.
"This isn't just another airplane," Defense Secretary Lloyd Austin said. "It's the embodiment of America's determination to defend the republic that we all love."
The B-21 is part of the Pentagon's efforts to modernise all three legs of its nuclear triad -- including silo-launched nuclear ballistic missiles and submarine-launched warheads -- as it shifts from the counterterrorism campaigns of recent decades to meet China's rapid military modernisation.
China is on track to have 1,500 nuclear weapons by 2035, and its gains in hypersonics, cyber warfare and space capabilities present "the most consequential and systemic challenge to US national security and the free and open international system," the Pentagon said this week in its annual China report.
"We needed a new bomber for the 21st century that would allow us to take on much more complicated threats, like the threats that we fear we would one day face from China (and) Russia," said Deborah Lee James, the Air Force secretary when the Raider contract was announced in 2015.
Partial presentation protects B-2 from prying eyes
While the Raider may resemble the B-2, once you get inside, the similarities stop, said Kathy Warden, chief executive of Northrop Grumman Corp., which is building the bomber.
"The way it operates internally is extremely advanced compared to the B-2, because the technology has evolved so much in terms of the computing capability that we can now embed in the software of the B-21," Warden said.
Other changes include advanced materials used in coatings to make the bomber harder to detect, Austin said.
"Fifty years of advances in low-observable technology have gone into this aircraft," Austin said. "Even the most sophisticated air defense systems will struggle to detect a B-21 in the sky."
Other advances likely include new ways to control electronic emissions, so the bomber could spoof adversary radars and disguise itself as another object, and the use of new propulsion technologies, several defence analysts said.
"It is incredibly low observability," Warden said. "You'll hear it, but you really won't see it."
Six Raiders are in production. The Air Force plans to build 100 that can deploy either nuclear weapons or conventional bombs and can be used with or without a human crew.
The B-2 was also envisioned to be a fleet of more than 100 aircraft, but the US Air Force built only 21 due to cost overruns and a changed security environment after the Soviet Union fell.
Fewer than that are ready to fly on any given day due to the significant maintenance needs of the ageing bomber.
The B-21 Raider, which takes its name from the 1942 Doolittle Raid over Tokyo, will be slightly smaller than the B-2 to increase its range, Warden said. It will not make its first flight until 2023.
However, Warden said Northrop Grumman had used advanced computing to test the bomber's performance using a digital twin, a virtual replica of the one unveiled Friday.
Ellsworth Air Force Base in South Dakota will house the bomber's first training program and squadron, though the bombers are also expected to be stationed at bases in Texas and Missouri.
A final noticeable difference was in the debut itself.
While both went public in Palmdale, the B-2 was rolled outdoors in 1988 amid much public fanfare. Given advances in surveillance satellites and cameras, the Raider was just partially exposed, keeping its sensitive propulsion systems and sensors under the hangar and protected from overhead eyes.
"The magic of the platform," Warden said, "is what you don't see."