Two skydivers freefalling at 120mph almost collided with two American fighter planes travelling at nearly 350mph over Chatteris airfield.

The near-miss incident - which saw two F15s pass directly under the skydivers - was caught on a camera that had been fitted to a parachutist helmet.

The pilots from the US base at RAF Lakenheath were not told that the Chatteris parachute site was active, according to a report from the UK Airprox Board.

The board was shown footage from the incident - which happened on April 17 at 1.17pm - and "could clearly see the F15s passing beneath, although it was difficult to assess the actual distance".

Since the incident the American air force has re-briefed all of its crews to make them aware of Chatteris airfield's status.

The Airprox report commended the "proactive measures" that had been taken to remind all the crews of the need to avoid the parachuting site and stated that "there was very little more that Chatteris could have done".

The report says "the F15 pilots should have known that Chatteris was active prior to getting airborne" and that "the crews did not see the parachutists and neither the crews nor the parachutists were able to take any action".

The report continues to say that the American fighters jets had made a turn shortly before to avoid a refuelling tanker and were "then handed over from air traffic controllers at RAF Coningsby to those at RAF Lakenheath.

"However, the frequency became busy just as they transferred and so, by the time the F15 pilots checked in with the controller, they were already about to fly over Chatteris."

Airprox said that several ground and flight elements were 'ineffective'.

These included that air traffic control did not advise the F15 pilots that Chatteris was active and that air traffic control did not brief the pilots to keep clear of Chatteris.

One of the F15 pilots told the inquiry that he took avoiding action from a KC135 jet that was on a collision course with the formation.

He was not aware that Chatteris airfield was active and that it was not mentioned by air traffic control.

The UK Airprox Board's objective is to enhance air safety in the UK, in particular in respect of lessons to be learned and applied from Airprox occurrences reported within UK airspace.

An Airprox is a situation in which, in the opinion of a pilot or air traffic services personnel, the distance between aircraft as well as their relative positions and speed have been such that the safety of the aircraft involved may have been compromised.