USAF hasn't solidified a final date but announced the unveiling event would take place at Northrop's facilities in Palmdale, California. 

"We are still working to nail down all the plans," Air Force acquisition executive Andrew Hunter said during a discussion with reporters at the Air Force Association's Air, Space, and Cyber conference, on Tuesday. 

Northrop disclosed that it has six B-21s in "various stages of final assembly" at the Palmdale facility, with the first flight scheduled for 2023. 

"The B-21 is the most advanced military aircraft ever built and is a product of pioneering innovation and technological excellence. 

"The Raider showcases the dedication and skills of the thousands of people working every day to deliver this aircraft," said Doug Young, sector vice president and general manager, Northrop Grumman Aeronautics Systems.

December's event will be the first time in 34 years Northrop has unveiled a stealth bomber. In 1988, Northrop gave the first public display of the B-2 bomber that flew the following year and was introduced into service in 1997.