London (CNN)A pair of skydivers narrowly avoided colliding with two US fighter planes traveling at almost 350 mph over the UK, a report has revealed.
The parachutists, who have not been identified, were in free fall at around 120 mph when the two F-15 jets passed beneath them on April 17.
The near miss -- or "airprox" as it is officially referred to -- was captured on a GoPro camera attached to the helmet of one of the skydivers, according to a report by the UK Airprox Board, which monitors such incidents. The parachutist assessed the risk of collision as "medium," the report's authors said.
The skydivers had taken off from Chatteris airfield in Cambridgeshire, while the jets set out from the Royal Air Force (RAF) base in Lakenheath, Suffolk, home to the US Air Force's 48th Fighter Wing. Weather conditions were good and the report stated that the skydivers had 10 kilometers visibility, while the pilots had a clear view for 50 kilometers.
Designated parachute drop zones must be marked on aviation charts, which means it is incumbent on aircraft operators in the area to know that skydivers could be in flight. According to the report, the RAF base received a call from Chatteris each morning to inform them of any activity.
One of the pilots told investigators that he was not aware that Chatteris was open to skydivers at that time and nothing had been mentioned by air traffic control (ATC). This should not have been the case, according to the report, and steps have since been taken to prevent further incidents.
The report, which was published in recent weeks, states: "When asked whether the pilots should be aware of Chatteris, the Board were told that it was included in their arrival training at Lakenheath, and that, as a result of this incident, the unit was re-briefing all of its crews to ensure they were all aware of its status."
There were several contributing factors, according to the report, which suggested that the breakdown in communication may have partly come about due to the heavy workload of Lakenheath air traffic control.
It stated: "The Lakenheath controller was aware of the position of Chatteris, and the Board were told that each morning Chatteris called ATC to advise when they are active; the paradropping aircraft also calls on the frequency when they are airborne with parachutists.