A drone flies over the scene of an explosion that leveled two apartment buildings in the East Harlem neighborhood of New York on March 12. (Mark Lennihan/AP)

Pilots around the United States have reported a surge in near-collisions and other dangerous encounters with small drones in the past six months at a time when the Federal Aviation Administration is gradually opening the nation’s skies to remotely controlled aircraft, according to FAA records.

Since June 1, commercial airlines, private pilots and air-traffic controllers have alerted the FAA to 25 episodes in which small drones came within a few seconds or a few feet of crashing into much larger aircraft, the records show. Many of the close calls occurred during takeoffs and landings at the nation’s busiest airports, presenting a new threat to aviation safety after decades of steady improvement in air travel.

(Related: Close encounters on rise as small drones gain in popularity)

Many of the previously unreported incident reports — released Wednesday by the FAA in response to long-standing public-records requests from The Washington Post and other news organizations — occurred near New York and Washington.

The FAA data indicates that drones are posing a much greater hazard to air traffic than previously recognized. Until Wednesday, the FAA had publicly disclosed only one other near-collision between a drone and a passenger aircraft: a March 22 incident involving a US Airways regional airliner near Tallahassee, Fla.

Since June 1, pilots of passenger airlines and other aircraft have reported 25 near-collisions with small drones across the United States.

The newly released incident reports, however, reveal that the FAA has been receiving a steady stream of near-miss alerts from airliners and private pilots since then.

On Sept. 30, air-traffic controllers at LaGuardia Airport in New York reported that Republic Airlines Flight 6230 was “almost hit” by a brightly colored small drone at an altitude of 4,000 feet as the passenger plane was descending to land. On Sept. 8 at LaGuardia, three different regional airliners — Express Jet, Pinnacle and Chautauqua — reported “very close calls” with a drone within minutes of one another at an altitude of about 2,000 feet as they were preparing to land.

On July 29, a US Airways shuttle flight that had departed from Reagan National Airport reported an extraordinarily narrow encounter with a yellow drone with a four-foot wingspan that suddenly passed within 50 feet of the aircraft while it was approaching LaGuardia.

Outside Washington, Porter Airlines Flight 725 from Toronto was descending to Dulles International Airport at an altitude of 2,800 feet on June 29 when it reported that a black-and-silver drone zipped past, just 50 feet away. On June 1, a United Airlines flight originating from Rome alerted the control tower at Dulles that a four-engine helicopter drone interfered with its descent and passed just 100 feet underneath the Boeing 767.

The 25 near-midair collisions were among more than 175 incidents in which pilots and air-traffic controllers have reported seeing drones near airports or in restricted airspace since June. Pilots described most of the rogue drones as small, camera-equipped models that have become increasingly popular with hobbyists and photographers.

Although such drones often measure only a few feet in diameter and weigh less than 10 pounds, aviation safety experts say they could easily trigger an accident by striking another plane’s propeller or getting sucked into a jet engine.

“The potential for catastrophic damage is certainly there,” said Fred Roggero, a retired Air Force major general who was in charge of aviation safety investigations for the service and now serves as a consultant to companies seeking to fly drones commercially.

Small aircraft proliferate

The reported increase in dangerous encounters comes as the FAA is facing pressure from federal lawmakers and drone manufacturers to move more quickly to open the skies to remotely controlled aircraft.

Under a 2012 law, Congress ordered the FAA to safely integrate drones into the national airspace. The FAA is still developing regulations to make that happen, a process that is expected to take years.

Under FAA guidelines, it is legal for hobbyists to fly small drones for recreational purposes, as long as they keep them under 400 feet, at least five miles away from airports and outside other restricted areas. Flying drones for commercial purposes is largely prohibited, although the FAA has begun to issue special permits to filmmakers and other industries to operate drones on a case-by-case basis until the agency can adopt a final set of safety regulations.

The FAA, however, is struggling to keep up with an influx of cheap drones that have flooded the market. According to some estimates, half a million small drones have been sold in the United States in the past three years.

The aviation-safety agency lacks the manpower to police airports or effectively track down offenders. Only a handful of rogue drone operators have been apprehended or penalized across the country.

In a statement, the FAA acknowledged that it is now receiving about 25 reports a month from pilots who have spotted drones flying in restricted airspace or in close proximity to other aircraft.

“In partnership with federal, state and local law enforcement agencies, the FAA has identified unsafe and unauthorized [drone] operations and contacted the individual operators to educate them about how they can operate safely under current regulations and laws,” the agency said.

Previously, the only other occasion in which the FAA has released data on drone sightings near airports came in June, when The Post reported that the agency had received a total of 15 reports of risky encounters over a period of two years — or an average of fewer than one incident a month.

Asked why there had been such a large increase in reports since then, the FAA said in a statement Wednesday that the difference could be “attributed to increased awareness by pilots and the public and improved reporting and record-keeping processes.”

Pressure to open the skies

Manufacturers and businesses that want to fly drones — including real estate agents, delivery firms, photographers and farmers — have criticized the FAA for moving too slowly to develop rules of the sky for using the new technology.

They say the absence of clear regulations for certifying drone pilots and aircraft has contributed to a rise in reckless behavior by untrained drone enthusiasts.

“The reality here is that we need to have rules,” said Michael Drobac, executive director of the Small UAV Coalition, a lobbying group for firms that make drones or want to integrate them into their business operations. He said “sophisticated companies” are largely prohibited from flying drones but that hobbyists can operate them without oversight.

Among the companies that are part of the Small UAV Coalition is Amazon.com, which wants to use autonomous drones to deliver small packages to customers’ doorsteps. (Amazon chief executive Jeffrey P. Bezos also owns The Post.)

Rapid advances in technology have made small drones affordable and easy for people to fly right out of the box. Some models cost less than $500. Most come with powerful miniature cameras that can film striking video scenes while hovering over back yards, stadiums, city centers and other places previously beyond the reach of amateur photographers.

R. Lee Morris, a professional photographer in Charleston, S.C., said he began flying a small DJI Phantom drone with a GoPro camera last year and was “blown away” by its capabilities. “It’s just an incredible thing to have fun with.”

In a blog post in March, he wrote that he wanted to see how high the Phantom could fly so he tested it over the skies in a populated area in Charleston. He estimated that the Phantom rose to about 1,000 feet — more than twice as high as the FAA guidelines for hobbyists — and acknowledged that it could have caused problems for rescue helicopters or low-flying aircraft.

In an interview, Morris said he felt a little guilty afterward and removed videos of the flight from his Web site because “I didn’t want to set a bad example.” But he added that he wasn’t convinced that flying a small drone like a Phantom posed an aviation hazard. He said a pilot friend told him that if the drone struck another plane’s propeller, the remotely controlled aircraft “would just explode into a million pieces.”

‘It was some idiot out there’

Several pilots who reported dangerous encounters with drones to the FAA disagreed strenuously, telling The Post in interviews that the tiny aircraft can pose a menace to air safety.

Drones are not equipped with transponders to broadcast their locations in the sky, and most models are too small to show up on radar or anti-collision warning systems. By the time they become visible at high altitudes, pilots said, it is usually too late to change course.

“All it’s going to take is for one to come through a windshield to hurt some people or kill someone,” said Kyle Fortune, who was flying a four-seat Cirrus SR-22 near Medford, Ore., on Sept. 22, when he said a drone about four feet in diameter suddenly appeared 100 feet underneath his plane.

He was flying at an altitude of 4,000 feet — about 10 times higher than the FAA’s height restrictions for small drones.

“It was some idiot out there with a drone. I have no idea what he was doing up there, taking pictures or whatnot,” Fortune said. “If it had come through the cockpit it wouldn’t have been a good day.”

Mike Gilbert, chief flight instructor at Aviation Adventures, a flight school based in Manassas, Va., was flying a Cessna with a student and another passenger about 9:45 p.m. on Sept. 17 when a small drone with two red lights suddenly appeared about 200 feet overhead.

“It came seemingly out of nowhere,” Gilbert said. “As pilots, at a minimum it’s distracting. If one of them hits us, we’re coming down. We’re trained to deal with dead engines, but we’re afraid it’s going to hit a [propeller], which would be a disaster, or the airframe.”

Several other near-collisions have been reported by pilots of rescue helicopters used to transport patients needing emergency medical attention.

A Life Flight helicopter in Pottsville, Pa., reported Nov. 19 that it was descending at 2,400 feet when a flight nurse in the co-pilot seat suddenly yelled: “Watch out!” A small drone was flying straight toward the rescue helicopter “at a high rate of closure,” according to a report that the crew said it filed with the FAA.

The pilot was forced to make a sharp banking turn to the right to avoid a collision, according to the report. The crew estimated that the drone passed with about 50 to 100 feet of separation.

Greg Lynskey, government relations manager for the Association of Air Medical Services, said small drones were becoming a major concern for rescue helicopter crews around the country. He said the FAA guidelines that allow hobbyists to fly drones as long as they stay five miles away from airports are too lax and do little to protect helicopters that fly near hospitals or pick up patients at accident scenes on the ground.

“I’m hoping this can get worked out before we have a catastrophic incident,” he said. “It wouldn’t take much to bring down a helicopter. If a drone hits the tail rotor, that’d pretty much be it.”

Concerned about the potential for trouble, drone manufacturers have begun to add software upgrades to their drone operating systems to prevent them from flying near airports or above a certain altitude.

DJI, the Chinese firm that makes the popular Phantom model, now programs its drones so that they cannot take off within 1.5 miles of a major airport and must stay below 400 feet within a five-mile radius of the installation.

The default height limit in other areas is programmed at 400 feet, although owners can bypass that ceiling by downloading a software application that comes with safety warnings.

“We did start noticing one of the challenges, or opportunities, we have is to program basic safe-flying practices into the firmware,” said Michael Perry, a DJI spokesman. “We all want to see this technology safely integrated into the airspace.”