"Continuous combat operations over the last 20 years have taken a toll on the airframe’s structure. Currently, a small portion of the B-1Bs are in a state that will require approximately ten to thirty million dollars per aircraft to get back to a status quo fleet in the short term until the B-21 comes online," the Air Force said in a press release.
The retirement, approved by Congress in the National Defense Authorisation Act, will trim the B-1 fleet to 45 active aircraft, with four of the retired planes required to remain in reclaimable condition, the Air Force said.
The replacement B-21 bomber promises a fifth-generation bomber with extended range and advanced stealth technology. Details remain shrouded in secrecy although reports in defence media publications suggest the aircraft will not come on line for another ten years.