File this under the category of "drone pilots trying to ruin it for everybody." According to a safety incident report published by the United Kingdom's Airprox air safety board, an Airbus A319 landing at Heathrow International Airport last September narrowly avoided a collision with a drone flying at an altitude of 500 feet as the jet was on its final approach. The pilots reported the small hovering helicopter-style drone passed about 25 yards to the left of the cockpit and just 20 feet above the aircraft.

The A319's wingspan is 112 feet, so that would mean the drone missed the airliner by as little as 30 feet. The pilot reported that there was no time once the drone was sighted to take evasive action. The pilot reported the drone to air traffic controllers, and the police were dispatched. However, the drone pilot was not found. The incident was classified as meeting risk category A—the highest level of incident covered by the reporting system short of an actual collision.

The drone was not detected by air traffic control radar, so the only details of the event and how close the aircraft came to striking the drone are the pilot's estimate of distance. In the UK, drones are limited to flight below 400 feet and are banned from flying in controlled airspace (like that around Heathrow) without permission from air traffic controllers. As the report noted, UK Civil Aviation Authority rules require a drone to stay within visual line of sight of the pilot—a maximum of 500 meters (1,640 feet) horizontally and 400 feet vertically from the operator.

This was hardly the only incident reported over London in the latest published details from UK Airprox. An Embraer E190 commuter jet had a less severe close call at an altitude of 2,600 feet over London just two days earlier, with a helicopter drone passing within 50 feet of its path. Less than a week later, a pilot of a Piper Cherokee reported a drone missing his aircraft by about 20 feet.

There were hundreds of these types of incidents reported in the US last year. Most recently, according to NASA's Aviation Safety Reporting System database, the pilot of a Bombardier CRJ200 commuter plane landing in Pittsburgh reported coming within 200 feet of a drone. "While on approach to PIT the captain noticed a drone and called its position out," the first officer noted in his incident report. "I looked up and saw a drone with a camera attached to the bottom pass no more than 200 feet above and to the left of the aircraft. We were descending through 500 feet at about 250 (nautical miles per hour) on the visual approach. It is obvious that catastrophic damage would have occurred to the aircraft if we would have struck the drone." The first officer also complained that somebody should be enforcing the FAA's regulations restricting drones flying near airports.