The OC-135B Open Skies United States Air Force observation aircraft supports the Treaty on Open Skies. The aircraft, a modified WC-135B, flies unarmed observation flights over participating parties of the treaty. Three OC-135B aircraft were modified by the Aeronautical Systems Center's 4950th Test Wing at Wright-Patterson Air Force Base in Ohio. The first operationally capable OC-135B was assigned to the 24th Reconnaissance Squadron at Offutt AFB in October 1993. It is now fitted with a basic set of navigational and sensor equipment, and placed in inviolate storage at the Aerospace Maintenance and Regeneration Center at Davis-Monthan Air Force Base near Tucson, Arizona. Two fully operational OC-135B aircraft were delivered in 1996 with the full complement of treaty allowed sensors, which i