The United States is speeding up production of its long-range B-21 Raider stealth bomber to take on challenges from China as the two countries tussle over the South China Sea and Taiwan . US Air Force secretary Frank Kendall told a conference in Maryland on Monday that the US had five of the bombers in production, up from the previously reported two. “As I speak there are now five test aircraft being manufactured on the B-21 production line at Air Force Plant 42 in Palmdale, California,” he said, addressing the Air Force Association’s Air, Space and Cyber Conference. “You will never hear me make optimistic predictions about programmes. All programmes have risk and the same is true of the B-21, but at this point at least, the programme is making good progress to real fielded capability.” Kendall said the challenge from China was growing and the air force must have a mix of aircraft, systems and capabilities to carry out any mission, anywhere, anytime. In July, US-based Defence News quoted Randall Walden, director of the air force rapid capabilities office, as saying the Raider was key to nuclear modernisation, a top priority for the service. The aircraft’s design approach set the nation on the right path to ensuring America’s enduring air power capability, Walden said. The air force plans to buy at least 100 B-21s, which can be armed with conventional and thermonuclear weapons and will start going into operation in the next five or so years. The air force plans to gradually replace the B-1 Lancer and the B-2 Spirit bombers to form a two-bomber fleet of B-21s and modified B-52s, another long-range strategic bomber that is being upgraded to remain in service for the next three decades. Zhou Chenming, a researcher at the Yuan Wang military science and technology institute in Beijing, said the US Air Force was accelerating the Raider’s production to upgrade its older equipment and increase the air force’s long-range ability to confront China and Russia. “There are five B-21s under construction, rather than the traditional approach of first building two aircraft for test flights and then building more to test performance and electronic equipment. This combines two steps into one,” Zhou said. “It shows that the United States is anxious and must speed up – it can’t follow the traditional process. “The B-2 now in service is outrageously expensive and too old ... The B-52 is also less able to confront China and Russia in the future … The B-21 is of great significance to the long-range strike capabilities of the force.” As tensions have risen over the South China Sea, the US has sent its B-2 and B-52 bombers on missions over islands claimed by China, Vietnam, the Philippines, and others in the region. Zhou said B-21s were expected to be used for such patrols in the future. He said China was developing its H-20 stealth bomber but its debut could be later than the B-21’s. Fewer H-20s were expected to be produced because China did not have the US’ global ambitions, he said.