The US Air Force has completed its critical design review of the Northrop Grumman B-21 Raider, marking another milestone in development of the next-generation stealth bomber.

The technical review, completed on 30 November, ensured the proposed aircraft has a stable and mature design before the USAF moves the programme into manufacturing and flight testing. The engineering and manufacturing development phase for the B-21 began almost three years ago, and the aircraft completed its preliminary design review in April.

Northrop Grumman B-21 Raider rendering

Northrop Grumman B-21 Raider rendering

Northrop Grumman

“The Air Force is pleased with how the programme is moving forward,” says Air Force secretary Heather Wilson. “The B-21 Raider programme is on the right track to make continued progress over the next few years as it now transitions from the design phase into a robust manufacturing phase that will ultimately produce our first B-21 test aircraft.”

The USAF plans for the strategic, long-rage bomber to achieve initial operating capabilities in the mid-2020s. The service plans to buy 100 B-21s – enough to retire by 2040 its fleet of 20 Northrop B-2 Spirit stealth bombers and 62 Boeing B-1B Lancer bombers.

The USAF plans to station B-21s at Dyess Air Force Base in Texas, Ellsworth AFB in South Dakota and Whiteman AFB in Missouri. Maintenance bases for the aircraft will be Tinker AFB in Oklahoma and Edwards AFB in California.

The stealth bombers were estimated to cost $564 million each, in fiscal year 2016 dollars. The service has not, however, provided an update cost estimate in recent years.