The U.S. 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.”

The Air Force instructed visitors in advance to turn in their mobile phones and that they would be able to see the plane only from at least 75 feet (23 meters) away. Photographers were told they could click away, but only from tightly controlled angles, reflecting the Pentagon’s determination to keep details of the bomber’s technology secret. It’s a step beyond the artist’s rendering of the radar-evading plane that was previously released.