Unlawful drone activity at Heathrow leads to runway closure.

In a harrowing near-miss incident, an unauthorized drone almost collided with an airliner traveling at nearly 200mph on Heathrow's primary runway, leading to its temporary closure, according to an official report.

The threat emerged when pilots of two commercial aircraft on their final approach detected the drone hovering at 3,000ft, alarmingly close to the airport. Air traffic controllers promptly informed the crew of a Finnair flight from Rome about the drone, positioned approximately three miles south of Maidenhead, Berkshire.

The UK Airprox Board, the entity responsible for investigating such incidents, mentioned in its report that the pilots chose to maintain their course, as the drone seemed to stay on the right side of their trajectory. As the aircraft approached the drone, it passed under the plane's left wing, dangerously close to the engine. The flight could have potentially carried up to 174 passengers.

Estimating the proximity between the drone and the plane to be 3ft to 10ft, the Finnair pilots classified the risk of a collision as 'high.' This encounter is considered one of the closest near misses involving a drone and an airliner in UK airspace.

The drone, described as round-shaped and sporting a purple/turquoise colour, was reportedly operating at over seven times the legal maximum altitude for drones of 400ft. Following the incident, air traffic control was alerted, and the Finnair plane landed safely on Heathrow's northern runway shortly before 12:40pm on April 8.

In the aftermath of the incident, the runway, known as RW09L, was closed to subsequent flights, which were rerouted to the southern runway, RW09R, to avoid any potential conflicts with the drone. The controller at Heathrow Approach deemed the action necessary due to the 'immediate risk' posed to other aircraft.

The UKAB, which categorizes near misses, rated the incident as a Category A - a classification reserved for the highest level of risk involving a serious collision threat. While the drone operator remains unidentified, the individual could face up to five years in prison for endangering an aircraft if apprehended.

The report stated: 'The Board considered that the pilot's overall account of the incident portrayed a situation where providence had played a major part in the incident and/or a definite risk of collision had existed.' An investigation by NATS (formerly National Air Traffic Services) found no trace of the drone on radar records.

This occurrence adds to a growing list of reported near misses involving drones and passenger aircraft over UK airspace, with many speculated to be rogue operators flouting altitude limits for sensational video footage.

Echoing concerns about the increasing drone-related hazards, a Finnair spokesperson said: 'Flying drones in areas where it is strictly forbidden shows that some drone enthusiasts have ignored safety regulations. We want to express our concern about this irresponsible activity. These cases endanger air traffic safety and can cause flight operations disruptions. Safety is the cornerstone of aviation, and we also expect a strong safety culture from drone enthusiasts.'

The two flights that initially reported the drone before the near miss with the Finnair aircraft are believed to have been a British Airways flight from Stuttgart, Germany, and an Aer Lingus flight from Cork, Ireland.