acted as a target for the new MiG-19 and MiG-21 interceptors to practice for the U-2. The "missile gap" The successful launch of Sputnik 1 on 4 October 1957 gave credence to Soviet claims about the progress of its intercontinental ballistic missile program, and began the Sputnik crisis in the United States. The U-2 intelligence caused Eisenhower to state in a press conference on 9 October that the launch did "not raise my apprehensions, not one iota", but he refused to disclose the U-2's existence as he believed that the Soviets would demand the end of the flights. In December 1958 Khrushchev boasted that a Soviet missile could deliver a 5-megaton warhead . Although the Soviets' SS-6 Sapwood missile program was actually stalled by technical failures, subsequent boasts—and U.S. Secretary of Defense Neil McElroy's statement in February 1959 to Congress that the Soviets might have a three-to-one temporary advantage in ICBMs during the early 1960s—caused widespread concern in the U.S. about the existence of a "missile gap". The American intelligence community was divided, with the CIA suspecting technical delays but the USAF believing that the SS-6 was ready for deployment. Khrushchev continued to exaggerate the Soviet program's success; the missile gap concerns, and CIA and State Department support, caused Eisenhower to reauthorize one Communist territory overflight in July 1959 after 16 months, as well as many ELINT flights along the Soviet border. British U-2 overflights were made in December and February 1960. The first one targeted a large segment of the railways in the Tyuratam test range area as ballistic missiles were expected to be deployed close to rail lines, as well as nuclear complexes and missile test sites. No sites were found. Neither flight proved or disproved the existence of a "missile gap". The British flights' success contributed to Eisenhower's authorization of one overflight in April. By 1960 U-2 pilots were aware, Knutson recalled, that Soviet surface-to-air missiles (SAMs) had improved and that overflights had become much riskier, but did not worry because "dumb fighter pilots always think it's the other guy that's going to get hit". By this time the CIA had also concluded internally that Soviet SAMs had "a high probability of successful intercept at providing that detection is made in sufficient time to alert the site". Despite the much-increased risk, the CIA did not stop the overflights as they were overconfident following the years of successful