The number of pilot mid-air sightings of drones has soared this year and is expected to more than quadruple by the end of 2015.
There were 650 sightings reported to the Federal Aviation Administration this year through August 9, compared with 238 through the whole of last year.
This figure includes commercial pilots and those at the controls of private planes and helicopters.
The use of personal drones is not outlawed but FAA rules ban drones from flying close to airports or at certain altitudes where aircraft operate.
The retail price of drones has fallen dramatically and trade groups estimate up to half a million drones have been sold in the US.
Some of the more sophisticated models can fly at speed several thousand feet above the ground.
In the past few weeks drones were spotted close to airports in Newark, New York and Minneapolis, the FAA said.
The dramatic increase in incidents comes despite a high profile campaign by the FAA and the commercial drone industry to guide users on ‘drone flying etiquette’ and aerial safety called ‘Know Before you Fly.’
However there seems to be little deterrent with few convictions for violating rules.
The agency has only settled five civil cases against unmanned flights.
