Two jumbo jets with around 1,000 people on board were just 100ft from crashing over Scotland because pilots confused their flight instructions, it has emerged.
The two Boeing 747s were 30 miles north of Glasgow and preparing to cross the Atlantic when an air traffic controller spotted they were moving closer together.
He immediately ordered the plane on the left to make a left turn and the one on the right to make a right turn to move them further apart.
But they did the opposite - bringing the two passenger jets closer together.
When the danger was first spotted the 747s were 10 miles apart, but within a minute they were three miles away and still closing in.
A crash was only averted when the two pilots on each aircraft saw each other and took evasive action, with one plane climbing and the other diving.
At one point, one plane was just 100ft above the other.
Details of the incident, which occurred on June 23 this year, were revealed in a report by the UK Airprox Board , which examines near misses in UK airspace.
Investigators are at a loss to explain how the crews of both aircraft either misheard or misinterpreted their orders.
The report said: "It was apparent that both crews had taken each others’ instructions, and the board found it hard to determine why this had occurred; unfortunately no human factor report was available from either crew.
"The board was surprised that all four pilots had misheard or misinterpreted the avoiding action instructions despite at least one of the crews reading them back correctly.
"One airline pilot member wondered if there could have been call-sign confusion; this was discounted because they were not similar ... the transmissions were clear on the RT recording."
The board said the danger was needlessly increased because the planes had earlier been ordered by air traffic control to fly at the same height of 34,000ft.