A passenger jet "narrowly avoided" a collision with a drone after take-off from Liverpool airport, according to an investigation from the U.K. Airprox Board (UKAB).
The watchdog's report found that "chance had a major part" to play with the Airbus A319 avoiding impact with what the pilot described as a large black and yellow drone.
UKAB reported, "Members agreed that this incident appeared to be a very near-miss and that the drone operator should not be flying in that location at that altitude."
The investigation concluded that despite the incident rated in the most serious risk category, the drone operator could not be found.
The number of incidents in which drones have narrowly missed collisions with passenger jets in the U.K. has increased almost 10-fold in less than 2 years.
UKAB had reported an increase from six other near-misses in 2014, though this figure has soared to 56 in the months up to October 2016.
In April this year, a British Airways flight due to land in Heathrow barely managed to avoid a drone while passing the tallest building in Western Europe, central London's The Shard.
A Heathrow spokesperson said in an email to CNBC on Thursday, "Anyone operating an unmanned aerial vehicle has an obligation to know the rules and ensure they are capable of operating it safely.
"Doing so in proximity to an airfield or aircraft is both illegal and clearly irresponsible," they added.