US Naval Air Systems Command (NAVAIR) provided an update on October 4 on the progress being made on conversion of a former Royal Air Force (RAF) Boeing E-3D Sentry AEW1 into an E-6B Mercury in-flight trainer for the US Navy.

The aircraft (former RAF serial ZH104) will have its outer mold line modified to resemble an E-6 while the aerial refueling probe and radar dome will be removed, as they are not required. It will however retain the receptacle for refuelling with the US Air Force (USAF) boom system, which will still be a requirement.

Once the maintenance and modifications are complete, flight-testing is scheduled to start in early 2024. The aircraft will help cut an estimated 600 flight hours and 2,400 landings/cycles per year from the E-6 mission aircraft. After retirement by the RAF, the aircraft had been in storage at Northrop Grumman's Lake Charles Maintenance and Modification Center at Lake Charles Airport, Louisiana, since January 2020. It was purchased by the US Navy under a contract signed on June 30, 2021.

At present, all initial and recurring E-6B pilot training flights uses E-6B mission aircraft. This means significant unnecessary wear-and-tear on operational aircraft and impacts on E-6B readiness and availability. It also increases the time required to train qualified aircrews for the E-6B mission.