RAF planes flying at low altitude through a Yorkshire Dales valley came within 200ft of colliding with a paraglider in a very rapid spin, an inquiry has concluded.

Air safety chiefs found a pair of two-seater turboprop Tucanos nearly hit the lightweight, foot-launched glider aircraft partly because they were focusing on flying at 45 degrees from one another, in a "fighting wing" formation.

The UK Airprox Board has rated the incident as among the more serious it investigated last year, and said the RAF aircraft, flying at 276mph, came so close to the paraglider that safety could have been compromised.

The independent board, which examines mid-air near misses, stated the RAF planes had been flying near the mountains of Whernside, Ingleborough and Pen-y-ghent shortly after 11am on September 17 when they encountered the adventure sport enthusiast 250ft above the ground.

The inquiry heard the first time the Tucanos, which are operated from No 1 Flying Training School, at RAF Linton-on-Ouse, near Thirsk, to provide basic fast-jet training to RAF and Royal Navy pilots, became aware of the paraglider was when a student pilot noticed "something going past rapidly on the right-hand side".

The report found none of the four crew in the Tucanos saw the paraglider until it was too late to take evasive action and one of the Tucano pilots had used the very rapid spin rate of the paraglider in his peripheral vision to assess the separation as "close".

While the Tucano instructor pilot assessed the risk of collision as "high" and said overcast conditions could have made it harder to see the hobby aircraft, the report stated the investigators had been unable to trace the paraglider pilot.

RAF chiefs said as the pilots should have anticipated such an incident as the area was regularly used for low-level military training and by hang-gliding enthusiasts.

The board concluded: "The onus was on the Tucano formation to give way to the paraglider,

and that the cause was that the Tucano pilots had seen the paraglider too late to increase separation,

effectively a non-sighting.

"Discussing the risk, members were convinced that the Tucano pilot’s description of rapid ‘spin-rate’ as the paraglider passed meant that safety margins had been much reduced below normal."