Part of the A4260 Oxford to Banbury road is expected to remain closed until Monday while RAF investigators search for clues as to why a Harrier jet crashed near Tackley.

Yesterday, as the pilot was revealed as flight lieutenant Chris Pearson, 100 RAF personnel, including a specialist aircraft recovery team from RAF St Athan, in South Wales, were drafted in to recover the remains of the GR9 jet and scour the surrounding area for debris.

There was speculation the jet crashed after striking birds.

A source working in the air industry locally, who did not want to be identified, said: "A vehicle was seen driving near Oxford Airport, which disturbed a flock of birds and the aircraft flew through that flock of birds. The crash happened half a minute to a minute later."

He said the birds were likely to have been sucked into the jet engine, causing it to fail.

It is thought the Harrier, which crashed at 5pm on Thursday, close to Upper Weaveley Farm, will be taken away for forensic examination either tomorrow or Monday.

Until then, RAF investigators will spend the weekend continuing the painstaking task of recovering parts of the £20m jump jet and trying to piece together its last moments.

An 800m stretch of the A4260, between Bunkers Hill and the Sturdy's Castle pub, will remain closed, along with side roads near the scene.

The Harrier was on its way to RAF Fairford, in Gloucestershire, from RAF Cottesmore, in Rutland, to take part in this weekend's Royal International Air Tattoo, when it got into difficulty and came down 150 yards from the pub.

Flt Lt Pearson, who ejected just seconds before the jet crashed, has been transferred from Oxford to the Queen's Medical Centre, in Nottingham, where he has undergone further tests.

He was not seriously injured and has been praised for averting a potential catastrophe.

An off-duty Thames Valley police officer, who was driving along the A4260 and whose car was struck by flying debris, has been discharged from hospital, but is still suffering shock.

RAF spokesman Squadron Leader Karl Mahon said: "The Harrier had a heavy landing and engineers have a significant task to recover the debris of the aircraft.

"Something serious went wrong, but until the investigation team have carried out their work we can't say whether it was technical or pilot fault - it would be wrong to speculate.

"What we do know is that because of his skill and professionalism the pilot was able to avoid a number of properties.

"Unfortunately, accidents happen and we lose aircraft. If he could have landed, he would have landed.

"A full, thorough and exhaustive investigation into the circumstances of the incident has begun."

Eyewitnesses saw the single-seater jet scream low overhead before its engines cut out.

Kalpesh Patel, 21, was at Oxford Airport, in Kidlington, for a pilots' course when he saw the plane go down.

He said: "We saw the Harrier in the air and saw a parachute appear. The plane just hit the ground and we saw the smoke. We were shocked, we couldn't really believe what had happened."

Once the plane is removed, the road will need to be resurfaced, because the fierce fire damaged the asphalt.

Oxfordshire County Council engineer Ralph Grant said: "At this stage, my advice to motorists would be to consider an alternative route around the area or to follow the diversionary routes which are in place."

I WAS DIALLING 99 WHEN PLANCE CRASHED When Tim Steer dialled 999 to say that a plane had crashed near Tackley, even the 999 operator seemed taken aback.

Mr Steer, 25, from Kirtlington, was one of the first people to call the emergency services after the Harrier jet crashed on Thursday afternoon.

He ran to the scene and took a picture with the camera in his mobile phone, inset, minutes after the plane had come down.

He said: "The plane crashed about a quarter of a mile from the field where I was walking my dog.

"I was dialling 999 as the plane was crashing and when I was asked what emergency service I wanted, I said I didn't know.

"When I said a plane had crashed, the operator was taken aback, but she took all the details."

Mr Steer, a medical co-ordinator at the John Radcliffe Hospital, in Oxford, said he was stunned as he saw the plane low in the sky, heading straight towards him.

"It was like you were standing on a runway watching a plane approach, its nose was raised. It's not the kind of thing you expect to see walking your dog."