The Electronic Frontier Foundation (EFF) filed a lawsuit against the U.S. Department of Transportation on Wednesday for allegedly withholding records pertaining to the use of unmanned aircraft within the United States.

"Drones give the government and other unmanned aircraft operators a powerful new surveillance tool to gather extensive and intrusive data on Americans' movements and activities," said EFF Staff Attorney Jennifer Lynch. "As the government begins to make policy decisions about the use of these aircraft, the public needs to know more about how and why these drones are being used to surveil United States citizens."

Any drone flying over 400 feet needs a certification or authorization from the Federal Aviation Administration, part of the DOT. But there is currently no information available to the public about who specifically has obtained these authorizations or for what purposes.

The group sent a Freedom of Information Act request to the DOT in April 2011, seeking to find which public and civil entities have been granted authorization to fly unmanned aircraft within the United States. Despite acknowledging the request, the agency failed to hand over any records.

The FAA has restrained the domestic use of unmanned aerial vehicles out of concern for the safety of U.S. airspace. But pressure is going on the FAA to make it easier for law enforcement agencies to gain permission to use unmanned aircraft.

There are hundreds of different models of UAVs, from large fixed-wing aircraft to a tiny drone called the Nano Hummingbird (pictured above). The drones employ a wide range of surveillance technology as well, including high-power zoom lenses, infrared and ultraviolet imaging, see-through imaging and video analytics. Some drones are also large enough to be fitted with weapons.

"The use of drones in American airspace could dramatically increase the physical tracking of citizens – tracking that can reveal deeply personal details about our private lives," said Lynch. "We're asking the DOT to follow the law and respond to our FOIA request so we can learn more about who is flying the drones and why."