The report, which has not been published, blames an air traffic controller at Seville for clearing one jet to descend through the flight level of the other one. It highlights how the Traffic Collision Avoidance System (TCAS), which warns pilots if they are on a collision course with other aircraft, alerted the pilot in time for him to take avoiding action.
But Britain's Civil Aviation Authority says it will take at least five years to bring in rules to make the carrying of TCAS mandatory because this would have to be agreed by the European authorities.
TCAS supporters, who include virtually all pilots, say Britain could at least ensure that all British airlines carried the equipment.
The incident occurred on 3 September last year and involved two Boeing 757s, a Monarch Airlines Boeing flying from Manchester with 244 passengers and crew and an Ambassador Airways aircraft from Gatwick with 242 passengers and crew. Both were heading to Malaga, with the Monarch aircraft at 37,000ft and, unknown to its pilots, the Ambassador aircraft directly underneath at 33,000ft.
According to the report, the Seville air traffic controller cleared the Monarch aircraft to descend first to 35,000ft and then to 11,000ft.
As it descended, the TCAS equipment sounded an alert and told the pilot to 'climb, climb now'. It was only as he began to do so that a gap in the clouds enabled him to see the Ambassador aircraft.
The report confirms that the aircraft were only 300ft apart vertically and that the risk of collision was category A, the highest.
TCAS is a radio system that enables the aircraft to detect any other aircraft at a set distance away, usually 16 nautical miles in front or 1,200 feet in vertical separation. It costs about dollars 200,000 (pounds 133,000) per aircraft to install.
UK aviation authorities initially argued that it caused a lot of false alerts. However, research by the Civil Aviation Authority has now shown that there would be an eightfold reduction in potential collisions if TCAS were installed on all commercial aircraft in British airspace.
Derek McLauchlan, the chief executive of National Air Traffic Services, has recently endorsed introducing TCAS, but says: 'It will take around five years to introduce TCAS as it has to be approved throughout Europe.'
The aviation authorities have also been concerned about two recent incidents in the UK which have highlighted the need for the TCAS equipment. Both, one in January and one in April, are being investigated by the Civil Aviation Authority and no details have been made available. But the two are expected to be assessed as Category A air misses, the most serious type, when the reports are published later this summer. Only eight Category A incidents involving commercial aircraft have occurred in British airspace since the beginning of 1991.
British Airways, which has TCAS fitted on about 80 of its 250 aircraft, says its pilots are very keen on the system being introduced on all its aircraft as soon as possible.Reuse content