On 9 April 1960, a U-2C spyplane of the special CIA unit 10-10, piloted by Bob Ericson, crossed the southern national boundary of the Soviet Union in the area of Pamir Mountains and flew over four Soviet top secret military objects: the Semipalatinsk Test Site, the Dolon Air Base where Tu-95 strategic bombers were stationed, the surface-to-air missile (SAM) test site of the Soviet Air Defence Forces near Saryshagan, and the Tyuratam missile range (Baikonur Cosmodrome).