The first prototype flew in 1964, and the aircraft entered service in 1970. It has an operational top speed of Mach 2.83 (Mach 3.2 is possible but at risk of significant damage to the aircraft and its engines) and features a powerful radar and four air-to-air missiles. When first seen in reconnaissance photography, the large wings suggested an enormous and highly maneuverable fighter, at a time when U.S. design theories were also evolving towards higher maneuverability due to combat performance in the Vietnam War. The appearance of the MiG-25 sparked serious concern in the West and prompted dramatic increases in performance for the McDonnell Douglas F-15 Eagle then under development in the late 1960s. The capabilities of the MiG-25 were better understood by the west in 1976 when Soviet pilot Viktor Belenko defected in a MiG-25 to the United States via Japan. It turned out that the aircraft's weight necessitated its large wings.