The UK's first near-miss between a passenger plane and multiple drones has been reported by pilots on jet flying into Heathrow airport.
Flight crew on the Airbus A320 spotted two large drones flying just a few hundred metres below them as they passed over East London.
The safety of the aircraft was "compromised" as a result of the distraction caused by monitoring the devices, according to a report into the incident by the UK Airprox Board (UKAB).
One of the two pilots on board also told investigators there would have been a "significant risk of collision" if the jet was on a different approach path to Heathrow.
The Civil Aviation Authority (CAA) said the incident on November 20 last year was the first aircraft near-miss involving more than one drone.
The pilots said the drone came within around 500 metres of the plane.
The report did not name the airline involved by said the jet was an Airbus A320 which can hold up to 180 travellers.
Less than half an hour after the near-miss, a Boeing 777 approaching Heathrow also flew within 50 metres of what is believed to be one of the drones.
The pilot saw an object that was white, around two metres wide and with four prongs.
A report was made to the Metropolitan Police but the drone operators could not be traced.
The UKAB investigation concluded that the unknown drone operator "had endangered the A320 and its occupants". However, given the distance a collision had been "unlikely".
There were five near-misses between aircraft and drones in the latest monthly UKAB report, bringing the total over the past 12 months to 62.
CAA rules state that drones must not be flown above 400ft or near airports or airfields.
In November it launched a website to publish its revised code of conduct for drones, called the dronecode.