Pilot reports of unmanned aircraft have increased over the past year, from a total of 238 sightings in all of 2014, to more than 650 by Aug. 9, 2015.

The U.S. Federal Aviation Administration (FAA) says it wants to send a clear message that operating drones around airplanes and helicopters is dangerous and illegal. It also says that unauthorized operators may be subject to fines and criminal charges, including possible jail time.

Pilots reported spotting 16 unmanned aircraft in June 2014 and 36 the following month. However, that number spiked in 2015: 138 pilots reported seeing drones at altitudes up to 10,000 feet during June, and another 137 in July.

The FAA says it will continue to work closely with industry partners through the “Know Before You Fly” campaign to educate unmanned aircraft users about where they can operate drone within the rules.

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