This public service announcement provided by the U.S. Forest Service shows a poster warning people not to fly drones near wildfires. (Associated Press)

Rogue drone operators are rapidly becoming a national nuisance, invading sensitive airspace and private property — with the regulators of the nation’s skies largely powerless to stop them.

In recent days, drones have smuggled drugs into an Ohio prison, smashed against a Cincinnati skyscraper, impeded efforts to fight wildfires in California and nearly collided with three airliners over New York City.

Earlier this summer, a runaway two-pound drone struck a woman at a gay pride parade in Seattle, knocking her unconscious. In Albuquerque, a drone buzzed into a crowd at an outdoor festival, injuring a bystander. In Tampa, a drone reportedly stalked a woman outside a downtown bar before crashing into her car.

The incidents are the byproduct of the latest consumer craze: cheap, easy-to-fly, remotely piloted aircraft. Even basic models can soar thousands of feet high and come equipped with powerful video cameras — capabilities that would have been hard to foresee just a few years ago.

Reports began surfacing last year of runaway drones interfering with air traffic and crashing into buildings. But the problem has grown worse as drone sales have surged.

The increase of cheap, easy-to-fly, remotely piloted aircraft buzzing around America's skies is becoming a nuisance. Drones have crashed into buildings, impeded efforts to fight wildfires and even landed on the grounds of the White House. Here are a few instances of rogue drones. (Jason Aldag/The Washington Post)

“I’m definitely getting much more concerned about it,” Michael P. Huerta, the head of the Federal Aviation Administration, said in a phone interview Monday. He said the FAA is particularly worried about a surge in reports of drones flying dangerously close to airports. The latest incident came Sunday, when four airline crews reported a brush with a drone on a flight path into Newark International Airport.

[When drones fall from the sky]

Huerta added that the recent interference by drones with California firefighters was “really a wake-up call for a lot of people. This kind of thing has got to stop.”

Most new drone models are aimed at novice fliers who are often “blissfully unaware” of aviation safety practices, said Michael Braasch, an electrical engineering professor and drone expert at Ohio University. “Unfortunately, there’s also going to be a small percentage of users who are just going to behave badly.”

The Consumer Electronics Association, an industry group, estimates that hobbyists will buy 700,000 of the remote-controlled aircraft in the United States this year, a 63 percent increase from 2014.

Although the vast majority of drone enthusiasts fly solely for recreation, authorities worry about the potential for a new airborne menace.

In a July 31 intelligence bulletin, the Department of Homeland Security said it had recorded more than 500 incidents since 2012 in which rogue drones hovered over “sensitive sites and critical installations,” such as military bases and nuclear plants. In one well-publicized case in January, a drone crashed onto the White House grounds.

Another unnerving scenario emerged last month when a Connecticut man posted an Internet video of a drone he had armed with a handgun, firing shots by remote control as it hovered in the air. Local police and the FAA determined that no laws had been broken.

In general, drone misadventures are happening in a regulatory vacuum. The FAA has banned most commercial drone flights until it can finalize new safety rules — a step that will take at least another year.

But people who fly drones for fun aren’t regulated. Under a law passed in 2012 that was designed in part to protect model-airplane enthusiasts, the FAA cannot impose new restrictions on recreational drone owners. As a result, they are not required to obtain licenses, register their aircraft or undergo training.

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To protect regular air traffic, the FAA has issued guidelines requiring that consumer drones stay at least five miles away from airports and below an altitude of 400 feet.

Those standards are widely flouted, however; in the past month alone, airline pilots have reported close calls with drones near airports in New York, Charlotte, Minneapolis and Phoenix.

In neighborhoods nationwide, the buzz of drones is becoming a common sound, as well as a source of conflict. Police blotters contain an increasing number of reports from residents complaining about uninvited drones hovering over their back yards.

For the most part, such flights are legal — a fact that is prompting a backlash from anti-drone vigilantes.

In Hillview, Ky., last month, a homeowner blasted a drone out of the sky with a shotgun, saying he was trying to protect his daughters from being spied on. He was charged with criminal mischief; police did not take action against the drone owner.

Similarly, in May, a judge ordered a man from Modesto, Calif., to pay a neighbor $850 for peppering his drone with buckshot. In September, a man from Cape May, N.J., was charged with shooting down a neighbor’s drone as it filmed houses along Seashore Road.

In other cases, however, authorities have been more sympathetic toward drone haters. In June, for example, prosecutors did not take action against a crew of firefighters in Orange County, N.Y., who used their water hoses to knock down a drone that had been filming them as they battled a house blaze.

In California last month, state legislators introduced a bill that would grant immunity to emergency responders who damage a drone that gets in their way. The measure was prompted by several incidents in which amateur paparazzi drones swarmed around wildfires, crowding the skies and forcing firefighters to ground their tanker aircraft to avoid a midair collision.

“Cars were torched on the freeways because drones made aerial firefighting efforts impossible,” state Sen. Ted Gaines (R-El Dorado), a sponsor of the measure, said in a statement. “This is maddening and I can’t believe that hobby drones are risking people’s lives to get videos on YouTube.”

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Although the FAA lacks the authority to license recreational drones, it does have the power to impose civil fines on anyone who recklessly interferes with air traffic or endangers people on the ground. Yet the agency has levied fines in only a handful of cases, saying it does not have the staff to investigate most complaints.

Huerta, the FAA chief, said Monday that the recent spate of risky incidents prompted the agency to revisit its approach and that it will adopt “more stringent enforcement” measures in cooperation with state and local officials.

For months, FAA officials had focused almost exclusively on trying to educate drone operators.

The agency has partnered with the drone industry and others on a public awareness campaign aimed at hobbyists called Know Before You Fly. The FAA has also co-sponsored public service announcements to discourage drone use at special events and locations, such as the Super Bowl, the California wildfires and a no-fly zone that covers much of the Washington region.

FAA officials said they are encouraging major retailers to provide drone-safety information to holiday shoppers this year. The agency also is testing a software application for Apple devices that would inform drone users whether it is safe or legal to fly at a specified location.

Drone manufacturers have made it easy for consumers to fly the robotic aircraft right out of the box. But companies need to take more responsibility for educating their customers by adding warning labels, devising software fixes to limit where drones can fly and taking other steps, said James H. Williams, a former manager of the FAA’s drone integration office.

“In a lot of ways, it’s up to the manufacturers to warn people about flying too high, flying too close to airports, flying too close to airplanes,” said Williams, now an aviation consultant for Dentons, a major law firm. “It’s important that they step up and do more than they are.”

Brian Wynne, the president of the Association for Unmanned Vehicle Systems International, an industry group, said that “there’s always room” for drone companies to expand education efforts. But he said there is only so much the industry can do to prevent reckless behavior.

“I frankly just don’t think there’s any excuse for anyone flying a [drone] anywhere near an airport or near a runway,” he said. “We have got to enforce our laws.”