New air traffic guidelines `not so safe'.

A DECISION to halve the vertical distance between passenger jets flying over Europe has been taken without properly assessing the risks, a leading air safety expert claimed yesterday.

Professor Peter Ladkin says the risks of flying in European airspace are not as low as the public has been led to believe.

His warning follows new flight rules brought in last year which cut the vertical separation between cruising airliners by half to 1000 feet.

Professor Ladkin,a computer scientist specialising in dependable systems at the University of Bielefeld in Germany, said experts making the change had an unduly optimistic view of the risk involved in closely stacking aircraft.

The new Reduced Vertical Separation Minima (RVSM)doubled the number of aircraft able to fly in the busy cruising air lanes between 29,000 and 41,000 feet.

Eurocontrol, the European air traffic control organisation,insists that the ability of modern aircraft to maintain precise altitudes means the new rules are safe.

But Professor Ladkin says Eurocontrol has failed to take into account unusual circumstances that might influence an aircraft's altitude. In particular,he points to the unpredictable response of pilots and air traffic controllers to automatic air collision warnings.

Professor Ladkin highlighted three cases -one mid-air collision in which 71 people died and two near misses -which exposed the potential risks associated with RVSM.

Two,including the crash last year between a Russian Tupolev jet and a Boeing 757 over Germany,involved collision avoidance systems.