A safety probe was underway yesterday after two passenger jets came within seconds of a mid-air collision over south Essex.

Disaster was narrowly averted as the two packed planes - a Boeing 737 and a 757 - passed close to each other 8,000ft above Brentwood.

Independent experts were today attempting to find out how the Munich-bound 737 and the 757, beginning its descent into Heathrow, came so close to each other.

Civil Aviation Authority spokesman Richard Wright stressed: "The investigators' first job will be to find out just how close the aircraft came to each other.

"The pilot is obliged to file a report to the investigation team - from the UK Airprox Board - once he realises the statutory distance apart from another aircraft may have been breached.

"Pilots are required to keep either 1,000ft apart in height from another plane or three miles away from each other horizontally."

Both aircraft were receiving a radar control service from the air traffic control centre at West Drayton in west London at the time of the incident which took place at 5pm on Thursday.

This is the third scare in as many months involving the airspace over south Essex.

In April, two Boeing planes came just four seconds away from disaster as they flew 24,000ft over Canvey and Southend.

This followed another incident in the skies above Loughton, involving a Boeing 737 and a Gulfstream jet.

This part of the county is in the Clacton Sector, known as one of the busiest areas for air traffic in Europe. Hundreds of planes each day pass overhead.

Mr Wright insisted: "There is no suggestion that the planes in this latest incident were on a collision course, but a full investigation will be held, the results of which will be published in full."

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