The B1-B Lancer will be phased out of service with the introduction of the B-21, although, concerns have been raised about the overall number of bombers in service

The B-2 Spirit (background) and older F-15 fleet will face different rates, with the former retained as part of the USAF's bomber force while legacy airframes of the latter are removed

Less than 190 operational F-22 fighters were delivered to the USAF, with the number available for use thought to be considerably lower now

The F-22 Raptors, highly sophisticated as they are, could well find themselves removed from service ahead of time, despite the huge expense in development, acquisition, and sustainment

Introduced in 1955, the B-52 has been a mainstay for the United States Air Force for decades, but is also expected to be axed before its centenary year

The B-21 Raider effort will see the production of 100 bombers intended to recapitalise the United States Air Force's nuclear deterrent capability

The F-35A - one variant of a three-type design that encompasses the most expensive military development effort of all time - is a key element of the USAF's future fleet

Lockheed Martin's F-35 programme is the most expensive (or lucrative) defence endeavour of all time and will be the backbone of US combat air power for the next generation

More than 1,700 F-35A aircraft are purportedly planned to be acquired for the USAF over the lifetime of the programme, however, it is likely that this figure will be reduced