Government agencies such as NASA and U.S. Customs and Border Protection operate aircraft-size military drones that take off from runways like airplanes. Labs in the United States have even built tiny drones that look like hummingbirds. But most drones resemble the radio-controlled aircraft and toy helicopters flown by hobbyists for decades, capable of taking off horizontally, vertically or by being thrown into the air like a trained falcon or hawk.

"To say they're all the same is not accurate at all,” said Kevin Lauscher, an industrial sales representative for Draganfly Innovations Inc.

The U.S. Federal Aviation Administration does not plan to permit drones armed with weapons in U.S. civilian airspace, according to an official quoted by the Washington Times. But state agencies, sheriff's offices and universities have already found more widespread use for drones that carry cameras for taking photos or video from above.