Bomber carries a similar "flying wing" shape to its predecessor, the B-2, and will be able to deliver both conventional and nuclear weapons around the world using long-range and mid-air refueling capabilities.
America's newest nuclear stealth bomber has 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 programme is classified.
As evening fell over the Air Force's Plant 42 in Palmdale on Friday, the public got its first glimpse of the Raider in a tightly controlled ceremony. 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, which includes 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.
"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, Russia," said Deborah Lee James, the Air Force secretary when the Raider contract was announced in 2015.
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.
US unveils B-21 Raider, a high-tech stealth bomber that can carry nuclear and conventional weapons and is designed to be able to fly without a crew on board pic.twitter.com/oS1106asYH— TRT World Now (@TRTWorldNow) December 3, 2022
'Incredibly low observability'
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 defence 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 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.
Both the Air Force and Northrop also point to the Raider's relatively quick development: The bomber went from contract award to debut in seven years. Other new fighter and ship programmes have taken decades.
The cost of the bombers is unknown. The Air Force previously put the price at an average cost of $550 million each in 2010 dollars — roughly $753 million today — but it's unclear how much is actually being spent. The total will depend on how many bombers the Pentagon buys.
"We will soon fly this aircraft, test it, and then move it into production. And we will build the bomber force in numbers suited to the strategic environment ahead," Austin said.
The undisclosed cost troubles government watchdogs.
Ellsworth Air Force Base in South Dakota will house the bomber's first training programme and squadron, though the bombers are also expected to be stationed at bases in Texas and Missouri.
US Senator Mike Rounds, a Republican of South Dakota, led the state's bid to host the bomber programme. In a statement, he called it "the most advanced weapon system ever developed by our country to defend ourselves and our allies."