The US Air Force gave a first, carefully controlled glimpse at its B-21 bomber Friday, shedding a bit of the secrecy surrounding the $203 billion program to build a fleet of 100 stealthy warplanes.

“The B-21 looks imposing,” Defense Secretary Lloyd Austin told about 600 invited guests at a Northrop Grumman Corp. plant in Palmdale, California, in an elaborately staged ceremony late in the day to unveil the aircraft. “But what’s under the frame and the space-age coatings is even more impressive.” He said the plane will have unmatched range and stealthiness so that “even the most sophisticated air-defense systems will struggle to detect a B-21 in the sky.”