AIR accident investigators are trying to establish how a vintage plane crashed at an air show, killing the pilot and navigator.Thousands of horrified spectators watched as the the 50-year-old Fairey Firefly nose-dived to the ground while performing a manoeuvre at Duxford airfield in Cambridgeshire on Saturday.

AIR accident investigators are trying to establish how a vintage plane crashed at an air show, killing the pilot and navigator.

Thousands of horrified spectators watched as the the 50-year-old Fairey Firefly nose-dived to the ground while performing a manoeuvre at Duxford airfield in Cambridgeshire on Saturday.

The dead men were named as father-of-three Lieutenant Commander Bill Murton, 45, and crew member Neil Rix, 29. Despite the tragedy, the event continued yesterday .

The aircraft was flying normally in sunny clear conditions before it rolled upside down and careered into a field close to the M11 motorway, well away from spectators.

Eye-witness Graham Boyd said: "It went into a rolling movement. The pilot appeared to be struggling to regain control but didn't have enough height to recover and the aircraft plunged into the ground."

Thousands of visitors were at the Imperial War Museum's annual Flying Legends airshow, which was so popular organisers had to close the gates to new arrivals early in the day.

The veteran Royal Navy plane, which entered service in 1949, was one of only a handful of airworthy Fireflies and had just resumed flying after a complete rebuild.

It was part of a fleet of vintage military aircraft based at the Royal Naval Air Station Yeovilton in Somerset, and had been due to fly at the Lowestoft Air Show on both July 31 and August 1, with Mr Murton also lined up as the pilot.

A Ministry of Defence spokeswoman said an investigation would be launched into the cause of the crash.

At a press conference following the accident, the director of the Imperial War Museum at Duxford said carrying on with the show was the "right decision'.

Explaining it was a "difficult call', Ted Inman said: "Initially there was a pause because our emergency cover was away at the accident.

"We had time to consider whether to continue with the show and on balance we felt that it was appropriate to do so when emergency cover was restored to the right level.'

Mr Inman maintained that Duxford's accident record since it started hosting air displays in 1973 was "very good' and that Civil Aviation Authority guidelines were followed at all times.

The pilot of the Firefly, Lt Com Murton, served in the Royal Navy for 21 years. Navigator, Mr Rix, was an aircraft fitter with the Royal Naval Historic Flight (RNHF).

Mr Murton, who was married with three children and lived in Somerset, was the Commanding Officer of 727 Squadron based at Roborough, Plymouth, Devon.

He was an experienced pilot who had been flying with the Royal Naval Historic Flight for three years.

Mr Murton, who was born and educated in south London, began flying at the age of 17.

Commodore Bill Covington, the commanding officer of RNAS Yeovilton, said: "Bill was a most experienced and respected naval pilot with well over 5,000 hours flying time to his credit.

"He was a wonderful man, a fine naval aviator who lived for flying. All of us are devastated by his death. Our thoughts and prayers are with his family and friends.'

Mr Rix, who was unmarried, had been with the RNHF for five years.

Commander Bryan Wood, the manager of the Flight, said: "Neil loved aircraft and flying and was particularly proud to be associated with the Firefly.

"He was a most popular member of the Flight and our thoughts are with his family and friends at this sad time.'

In a report from the Air Accidents Investigation Branch (AAIB), issued earlier this week, investigators recommended a review of current arrangements at Duxford airfield to prevent aircraft landing or aborting take-offs from running on to the M11.

It followed an accident on June 2, 2002, when a former Soviet air force two-seat L-39 military jet trainer aircraft came to rest on the motorway after going through the boundary fence while landing.

At the Flying Legends airshow in 1996 the pilot of a Lockheed P-38J Lightning aircraft died when it crashed on the airfield while taking part in a formation event.