AIR accident experts have ordered a sweeping series of safety improvements after an US fighter almost collided with a passenger plane heading for a North-East airport, it was revealed last night.

The KLM Fokker 50 plunged towards the ground as it went into an emergency dive to avoid the oncoming F15 Eagle front-line strike aircraft travelling at almost 500mph.

Then it climbed steeply and, as air traffic controllers looked on helplessly, the fighter passed beneath the passenger plane - the US airmen apparently unaware how close they had come to disaster.

None of the 37 passengers was hurt as they had been asked to fasten their seat belts seconds before the near-miss south-east of Teesside Airport.

But many of them were left frightened and shaken as the KLM flight, from Schipol airport in Amsterdam, manoeuvred desperately to avoid a crash.

As the plane dived, then climbed steeply, passengers aboard suffered gravitational pull of almost 2G - similar to the forces experienced by Formula One racing drivers.

The US jet was on a training exercise heading south to RAF Lakenheath in Suffolk.

The near-miss came less than six months after a similar incidence involving a Shorts SD-360 heading for Newcastle Airport and an RAF Tornado F3.

Last night, the Civil Aviation Authority said wide-ranging safety measures had been put in place to reduce the risk over North-East skies. They include:

l Fitting transponders to military aircraft which send out an easily identifiable signal;

l A new protocol requiring military pilots to warn Newcastle Airport when operating in the area;

l The creation of an "airspace buffer" between military and civilian traffic for all major fighter exercises;

l The deployment of a military liaison officer to Newcastle Airport during big exercises who can advise on unusual radar contacts.

The terrifying near-miss at Teesside happened on August 13 and the improvements were in place by October last year.

But a report into the incident carried out by the Air Accidents Investigation Branch revealed that, despite the improvements, another near-miss happened in the same area on April 22 this year when a Norwegian DHC-8 came within 400ft of a Royal Navy Sea Harrier.

A report on this latest incident is expected soon.

The CAA's inquiry into the first Teesside scare says that despite the safety improvements, "there is clearly still a level of risk associated with the current airspace arrangements".

An inquiry is now under way to find more long-term measures to prevent commercial planes and military aircraft using the same airspace.

Its findings will be published at the end of this month.

Both the region's airports have exclusion zones which require military aircraft to contact flight controllers before they enter.

The issue of military aircraft using the North-East's increasingly crowded airspace has become a hot topic following a series of close encounters in recent years