It should have surprised no one that the FBI has a secret fleet of spy planes it uses domestically to watch us, as the Associated Press reported this week. WIRED published a story about surveillance aircraft spotted flying in unusual patterns in California and Virginia back in 2006. And the Wall Street Journal reported last year that the US Marshals Service has surveillance planes that use so-called "dirtboxes" to track mobile phone users on the ground.

But long before this, the New York Police Department had a high-tech surveillance helicopter that it obtained in 2003 through a government grant and exposed publicly to the media that year when it gave journalists a tour of the $10 million toy.

WIRED began investigating the chopper in 2008, and uncovered, but hasn't published until now, information about the precise surveillance components installed on it and the methods the NYPD used to conceal its ownership and operation. Like the FBI, the NYPD used a shell company to register the aircraft. But the NYPD also requested special "undercover" registration handling from the FAA to thwart tracking by aviation enthusiasts who might spot it in the air and attempt to investigate the registration number associated with it. The NYPD also asked the FAA to notify its aviation unit if anyone contacted the agency inquiring about the aircraft.

This raises serious questions about how many agencies are operating them in the US and how exactly they're being used.

Last month, the issue of secret law enforcement aircraft began getting attention after plane spotters around the country began reporting suspicious aircraft registered to shell companies that were flying unusual routes over numerous cities.