The first two-seat Starfighter model, the F-104B was ahead of its time in not receiving a TF designation, suggesting it was fully combat-capable. However, the F-104A's 20-mm cannon was omitted and internal fuel reduced. There were also quite a few other changes, and the definitive, FY 1957 machines had a 25 percent larger tailfin and rudder than the F-104A.