called for longer range via drop tanks, the P-38 was already equipped with fuel lines, hardpoints, and a supply of drop tanks. One famous example of these drop tanks was in Operation Vengeance, April 1943, when P-38Gs needed extra range to intercept and kill Admiral Isoroku Yamamoto. North Atlantic ferry operation In January 1942, a month after the United States declared war, Kelsey was promoted to the temporary rank of lieutenant colonel. In the spring of 1942 Kelsey was attached to the VIII Fighter Command at Dow Field near Bangor, Maine to assist in preparing for trans-Atlantic ferry flights in support of Operation Bolero. As an acting colonel, Kelsey was assigned to the 14th Fighter Group for the purpose of flying one of the group's fighters and for making sure preparations were sufficient. In July, with the call sign Shoe Black 7, he flew a P-38F in the first ferry flight of fighters across the North Atlantic to England. Returning to the States in September 1942, he resumed his former position as chief of the Pursuit Branch, and the following July he was named chief of the Flight Research Branch, Flight Test Division. Going to England in November 1943, Kelsey was deputy chief of staff of the IX Fighter Command, and the following February he was appointed chief of the Operation Engineering Section of the Eighth Air Force Headquarters. In February 1945 he was assigned to the Materiel Division at Air Corps Headquarters. Staff roles After Germany surrendered, Kelsey was assigned to the Materiel Command at Wright Field as chief of the All-Weather Operations Section. He reverted to the permanent rank of major in 1946, and from December 1946 to January 1948 he served successively as assistant deputy commanding general for personnel; deputy commanding general for personnel, and chief of personnel and administration. Returning to Air Force Headquarters in February 1948, Kelsey was chief of the Control Group in the Office of the Deputy Chief of Staff for Materiel. Kelsey attained the permanent rank of colonel in April. Entering the National War College in August 1948, he graduated the following June and remained there as an instructor. In June 1952 he was appointed Deputy Director of Research and Development in the Office of the Deputy Chief of Staff for Development at Air Force Headquarters, and was promoted to brigadier general in September. X-15 In October 1954, Kelsey was a key