The B-21 has been shrouded in secrecy since the Air Force chose Northrop over Boeing to build the plane in a hotly contested competition in 2015. Unlike other classified programs, the Pentagon openly acknowledges the new bomber’s existence — but that’s about it. The Air Force has kept most information about the plane a secret so that potential adversaries such as China and Russia cannot steal its design or develop ways to shoot it down. What the public does know is that the B-21 is built with a new generation of stealth technology designed to evade the most sophisticated radars....