In February 1944 the 56th FG began employing 150-gallon drop tanks on missions, enabling them to escort heavy bombers to the target area on deep penetration missions. The 56th was assigned a patrol sector west of Hanover in the vicinity of Dümmer Lake, and there on four missions in February and March Johnson shot down eight more German planes to become the leading U.S. ace at the time. Johnson's 200-hour combat tour was nearly over and he applied for and was granted a 25-hour extension of his tour. Promoted to captain on March 15, he scored three more victories before being transferred to the 62nd Fighter Squadron to act as its operations officer (S-3).