Concerned about an increase in pilots reporting encounters with unmanned aerial systems (UAS), the U.S. Federal Aviation Administration (FAA) wants drone pilots to understand that operating their aircraft around manned aircraft is dangerous and illegal.

While the FAA said unauthorized UAS operators can face stiff fines and criminal charges, including possible jail time, catching them remains problematic.

FAA spokesperson Les Dorr told UAS Magazine: “As you can appreciate, it’s a challenge when we get a pilot report and sometimes the report is not very specific. Even when it is specific—say the pilot says ‘I saw a quadcopter 200 feet off my port wing and I was 3.5 miles from the end of the runway’—that’s still a pretty big area in which to try to identify the operator.”

Dorr described the action the agency takes in such circumstances.

“What we would typically do is notify the appropriate law enforcement organization and have them try to see if they could identify the operator—but it is a challenge,” he added.

Brian Wynne, president and CEO of the Association for Unmanned Vehicle Systems International (AUVSI), said the organization supports enforcement action against careless and reckless UAS operators who violate restricted airspace.

“Stricter enforcement will not only punish irresponsible operators, it will also serve as a deterrent to others who may misuse the technology,” he noted.

Last year, the FAA said it received a total of 238 UAS sightings from pilots, but this year had received 650 such reports by early August. The agency said it has levied civil penalties for a number of unauthorized flights in various parts of the country, and has dozens of open enforcement cases.

Asked how many and what types of penalties the FAA has levied, Dorr checked with the FAA’s general counsel, and responded: “We have initiated more than 20 enforcement cases. We have settled five cases in which operators paid civil penalties. We have proposed penalties in at least five other cases. Several of the cases involve UAS operating near other aircraft.”

The FAA said pilots reported seeing 16 unmanned aircraft in June of 2014, and 36 the following month. This year, 138 pilots reported seeing drones at altitudes of up to 10,000 feet during the month of June, and another 137 in July.

In addition, the agency said firefighters battling wildfires in the western U.S. have been forced to halt operations on several occasions for safety reasons when they spotted one or more unmanned aircraft in their immediate vicinity.

Wynne called on the FAA to finalize its small UAS rules, which would require all UAS operators to follow the safety programming of a community-based organization or abide by new UAS rules for commercial operators.

“Once the rules are finalized, consumers will no longer be able to fly without any oversight or education,” he said.

The FAA said it will continue to work closely with industry partners through the “Know Before You Fly” campaign to educate UAS users about where they can operate within the rules. The agency is also supporting the National Interagency Fire Center’s “If You Fly, We Can’t” efforts to help reduce interference with firefighting operations.

The agency also said it’s working closely with the law enforcement community to identify and investigate unauthorized unmanned aircraft operations. The FAA encourages the public to report unauthorized drone operations to local law enforcement and help discourage dangerous, illegal UAS activity.