In January 1921, McClelland attended the Air Service Communications School at
Fort Sill, Oklahoma, and after graduation, remained there as an instructor. In February 1922, he was assigned to the Signal Corps radio laboratory at
Camp Alfred Vail, New Jersey, as Air Service representative and from August 1922 to February 1924, was officer in charge of the laboratory. Enthusiastic Air Corps booster Major
Benjamin Foulois, commander of Mitchel Field, arranged for a USAAC pilot to fly over and drop
baseballs for
Babe Ruth to catch. Ruth came out to Mitchel Field on July 22, 1926, dressed up in an Army uniform (he was in the
Reserves) to keep his end of the bargain. In the sweltering heat and humidity of a
Long Island summer, in front of a row of newspaper and film cameramen, as well as radio and print reporters, McClelland flew over Ruth at a speed of and a height of about . Foulois recalled that the first two baseballs that McClelland dropped near Ruth "knocked him flat" but that the third ball was caught with a shout of pain and then handed to the major. Foulois wrote in 1980: "The last I saw of the Babe that day he was slowly flexing his burning hand and trying to smile about it as he left in a big limousine." McClelland returned to the U.S. in July 1942 and was assigned to Headquarters Army Air Forces, Washington, D.C., where he was director of technical services until March 1943. After serving the next several months as deputy assistant chief of Air Staff, operations, Headquarters Army Air Forces, he became the air communications officer in July 1943. ==Postwar==