Snip . . . Twenty-five miles due south of Salt Lake City, a massive construction project is nearing completion.  The heavily secured site belongs to the National Security Agency.

Because the Utah Data Center is a "secure facility" and you cannot go inside without the needed security clearances, Fox News rented a helicopter and took to the skies, where the depth and breadth of the Utah Center were stunning.

The aerial video footage is exclusive to the Fox News investigation and posted here.  Two weeks after our filming, the helicopter pilot reported to our Fox News team that he had been visited by the FBI on a "national security matter."

The pilot said, according to the FBI agents, that the NSA had taken photos of the helicopter once it made several flyovers.  These photos allowed the NSA to identify the make and manufacturer of the helicopter in California who, in turn, told the NSA who operates it in the Salt Lake City area.

The FBI wanted to know if we had the proper air space clearances to flyover the site, which the Fox News team did.  Satisfied that the pilot was not flying "terrorists" over the site, the questioning concluded.  While the pilot passed along the Fox News contact information, there was no further inquiries.

Binney said the helicopter incident "showed the capability of the U.S. government to use information to trace people, their relationship to others and to raise suspicions about their activities and intentions."