RAF Valley Hawk jets in near miss over mid Wales
Two RAF Valley aircraft came within 100m (330ft) of each other in a near miss above mid Wales, says a report.
It happened on 1 February as the two Hawk jets from Anglesey were both on training missions near Aberystwyth.
The report by the UK Airprox board, which monitors near misses, says a collision at 16,000ft (4,900m) was only avoided by good luck.
Both pilots, who were trainees, took evasive action but it brought the jets closer together, it said.
Using information from both pilots and air traffic controllers, the report said that initially the Hawks were flying at different heights.
When one descended, onboard instruments warned each aircraft the other Hawk was approaching and both took evasive action.
However, this brought them closer together, said the report.
The pilots did not actually see each other until one reported seeing "a flash of black" as one passed the other.
The incident, which was over within a few seconds, ended with the aircraft within 100m of each other.
"[In any case], neither crew saw the other aircraft in time to take any avoiding action; the cause was, effectively, non-sightings by both crew," the report concluded.
"It was apparent from radar recordings that the aircraft had passed in close proximity," it added.
"The board were persuaded by the Hawk T1 pilot's statement that he had seen 'a flash of black, R (right) to L (left) across the front of the aircraft' that separation was reduced to the minimum and that the aircraft had avoided collision by providence."
The Ministry of Defence said it would not comment on individual cases.
However, a spokesman added: "The UK has a variety of measures in place to enable freedom of airspace use for all whilst ensuring that some of the most highly congested airspace in the world is also amongst the safest.
"Millions of flights are made in UK airspace each year but, despite that, just 184 air proximity reports were made in 2012 of which 10 identified that the safety of our aircraft may have been compromised further underlining the general effectiveness of UK airspace management and the professionalism of the commercial, military and private aviators that use it."