In 1960, both the U.S. Air Force and the U.S. Navy were developing requirements for new fighters. The Air Force was planning to replace the F-105 with a long-range, low-level supersonic, all-weather Tactical Strike Fighter to be operated from unpaved runways of 3,000 feet or less in length and capable of transatlantic ferry without refueling. The Navy needed an all-weather, carrier-based Fleet Defense Fighter with a big radar and six long-range air-to-air missiles. In 1961, these similar “Fighter” requirements were merged by the Secretary of Defense into one program, TFX, to save development costs and operating costs.