At the height of the cold war, as critics of the Eisenhower administration complained about the growing "missile gap," the United States secretly gathered data on Soviet missile capabilities through photographs obtained from U-2 reconnaissance plane overflights of the Soviet Union. In May 1960, plans were finalized for a crucial Paris summit conference between western nations and leaders of the Soviet Union with disarmament to be the main focus. Hopes for a successful summit were dashed when on May 1, May Day, an American U-2 spy plane piloted by Francis Gary Powers was shot down over Soviet air space. On the first day of the Paris summit, Soviet Premier Nikita Khrushchev stormed out after delivering a condemnation of U.S. spy activities.