The Flight Engineer became the Air Engineer in 1951 around the same time that the 1946 Aircrew Scheme was scrapped (only the Master Aircrew rank remains). The Flight Engineer Flying Badge became the Air Engineer Flying Badge in the new Queen’s Regulations shortly after.
The next change for the Air Engineer was when it was subsumed into the Weapon Systems Operator (WSOp) cadre - as a WSOp (A Eng). When the E3D Sentry goes out of service (which may be quite quickly if the rumours of the Defence Command Paper are true - due out this Monday) then that will be the last pure Air Eng role on an RAF aircraft. The last few Air Engs will either need to retrain for other WSO/WSOp roles or be used in flying related roles (like Air Safety). A few Air Engineers have already retrained in Air Loadmaster, Mission Systems Operator and Sensor Operator roles - thus proving the worth of the Weapon Systems Officer and Weapon Systems Operator vision where mission aircrew can retrain for a variety of roles and use their previously learned expertise too.