In January 2015, USAF officials told lawmakers that it would take 15 years to fully develop a new attack aircraft to replace the A-10; that year General Herbert J. Carlisle, the head of Air Combat Command, stated that a follow-on weapon system for the A-10 may need to be developed. It planned for F-16s and F-15Es to initially take up CAS sorties, and later by the F-35A once sufficient numbers become operationally available over the next decade. In July 2015, Boeing held initial discussions on the prospects of selling retired or stored A-10s in near-flyaway condition to international customers. However, the Air Force then said that it would not permit the aircraft to be sold.