As America’s secretive new stealth bomber, the B-21 Raider, continues development, it’s clear that the days of America’s legacy bomber platforms, the B-2 Spirit and the B-1B Lancer, are numbered. With the B-21 expected to enter into service in the mid-2020s, America’s current heavy payload stealth bombers and heavy payload supersonic bombers will begin their transition into retirement, gone the way of previous legendary aircraft like the SR-71 Blackbird or the F-117 Nighthawk.

Of course, when looking toward the future, we need to be careful not to discount the present, and if you ask the Air Force, America’s only mach-capable heavy payload bomber, the B-1B Lancer, has a whole lot of fight left in it. As the B-21 program works to render the “Bone” obsolete, the Air Force has plans to inject new life into the bomber to make sure it remains a viable platform well after the B-21 takes to the skies.

There’s good reason for this seemingly two-faced approach to bomber strategy. As one part of the Air Force endeavors to replace the B-1B, another aims to keep it at the forefront of combat technologies long enough to ensure Northrop Grumman has time to produce enough B-21s to replace both fleets of bombers. With 62 operational Lancers and 20 B-2s in America’s inventory, that may take some time. The B-21 may be expected to enter combat in the mid-2020s, but chances are good that the B-1B will have to stay in the fight for at least another decade thereafter.

“Once sufficient numbers of B-21 aircraft are operational, B-1s will be incrementally retired. No exact dates have been established,” Air Force spokesperson Maj. Emily Grabowski said. “The Air Force performs routine structural inspections, tests and necessary repairs to ensure the platform remains operationally viable until sufficient numbers of B-21s are operational.”