A FORMATION of 622mph maximum speed RAF fighter jets came within 100ft of smashing into a glider which had switched its identification signals off to prolong a flight, it has emerged.

Investigators have found one of the two combat aircraft was forced to perform an outside loop acrobatic manoeuvre just 1,000ft above the ground near Ripon after a Hawk wingman spotted the white one-seater sailplane against a white cloud background "on a pure collision course".

A report by the UK Airprox Board, which examines incidents in which the distance between aircraft as well as their relative positions and speed may compromise safety, concluded the incident on July 16, had been among the most serious it investigates.

It is understood the RAF planes had taken off from RAF Leeming, near Bedale, shortly before and the ASG29 glider had set off from near Thirsk and had flown over the northern Yorkshire Dales, before the near miss at 2.11pm.

The pilot of the Hawk, which is cleared to carry cluster bombs, air-to-air missiles and a cannon, reported visibility to be 24 miles and asked Leeming radar operators about air traffic, but the glider was not displayed on the Leeming radar screen.

The report states: "It was only the Hawk wingman visually acquiring the glider, albeit at a late stage, that had prevented a much higher risk event; his pro-active lookout and warning to his formation leader, who saw the glider even later and bunted to pass below it, were commended by the board."

After passing directly under the glider with 100ft separation, the Hawk pilot described the risk of collision as "very high".

The board found the glider pilot did not use his radio to contact an external agency as ‘he did not want the possibility of being ordered to go in a direction that he did not want to go in whilst maintaining Class G airspace’.

The report adds as the one-seater sailplane's batteries were not sufficiently powerful to supply the transponder, a device that emits an identifying signal, for its anticipated five-hour flight, the safety device was switched off.

A recent meeting of the Regional Airspace User Working Group hosted by RAF Leeming discussed and encouraged the use of radios and other electronic aids to improve situational awareness.

The meeting heard the belief that glider pilots would be ordered to take military air traffic control directions that they did not want was incorrect.

The board said the incident would be used as a case study to reinforce the mutual benefits of using safety devices such as strobes, transponders and radios.