On 10 January 1921, he was ordered to Hampton Roads, Virginia, to serve for eight months as executive officer of the Naval Air Station, Naval Operating Base. The Bureau of Aeronautics was established in the Navy Department on 1 September 1921, and on 21 October, Commander Ellyson became head of the plans division of that bureau. He remained in that assignment until December 1922, when he became the aviation member of the U.S. Naval Mission to Brazil, cooperating in the reorganization of the Brazilian Navy. He returned to the Bureau of Aeronautics in May 1925.