This particular CN-235, with the serial 96-6042, is one of six that researchers commonly associated with the Air Force's top secret 427th Special Operations Squadron... The 427th occupies the same space with a host of other "black" U.S. military aviation elements, most of which are affiliated to some degree with Joint Special Operations Command and the Intelligence Community... [I]f the military placed the aircraft under civilian control to some degree and with an appropriate legal justification, the U.S. military could possibly fly it in support of a domestic operation or one focused on a foreign suspect or organization operating within the United States... It's also entirely possible, if not probable, that the aircraft could be involved in a realistic training exercise rather than an actual operation... The area could have simply provided a suitable urban area to test existing or new surveillance technologies, too, though this could spark serious privacy concerns if true.
Friday an Air Force Special Operations Command public affairs officer confirmed that the plane was one of theirs, describing its activity as "just a training mission," according to Russia Today.