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.

“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.

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.

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 backyards.

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

In Hillview, Kentucky, 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, California, to pay a neighbor $850 for peppering his drone with buckshot. In September, a man from Cape May, New Jersey, was charged with shooting down a neighbor’s drone as it filmed houses along Seashore Road.