The Federal Aviation Administration is writing new rules to allow the use of unmanned aerial vehicles, more commonly known as drones, in domestic American air space for the first time.

But critics are raising privacy and safety concerns over how they may be used.

"Safety is our first priority," said Chris Stephenson of the National Air Traffic Control Association. "We understand that unmanned aircraft are on the horizon, in fact they're pretty much a horizon headed for the front porch."

What has many worried is what happens if a drone loses contact with its ground controller, becoming a wandering threat to commercial jetliners carrying dozens, if not hundreds, of passengers.

"We have to develop onboard sensors, radars and other sensors, that will alert the aircraft to an impending midair collision and maneuver to avoid that collision before it ever happens," said John Appleby of the U.S. Department of Homeland Security.

Congress has required the FAA to issue rules governing the use of drones in domestic airspace by 2015 — though a small number are already in use by the Department of Homeland Security. A small fleet of Reaper drones operate along the Mexican and Canadian borders.

But UAV manufacturers envision a far broader use-case. Some examples would be power companies who have to inspect long-distance transmission lines and farmers and ranchers trying to inspect fields and livestock.

Vanguard Industries, in Texas, has approval to conduct a demonstration project with it's miniature-helicopter like drone designed for use by law enforcement. It can be equipped with a shotgun, in addition to its kevlar-lined fuel tank. It's perfect for long-term surveillance and some believe it could also be helpful in a search for missing children.

"You can put the aircraft up at 400-500 feet, be able to scan the area for other individuals, and contain the area more visibly from the air than you can from the ground," said Mike Buscher of Vanguard.