A British Airways Boeing 757 and a Virgin Express Boeing 737 missed by just 200ft in dense fog over Heathrow Airport during the incident in August 1997. A catastrophe was only averted because one controller overheard a colleague directing one plane into the other's path. But the trade unions that represent the controllers blamed the heavy workload and called for more resources to be pumped into the system.
The news of the near miss is another blow to the reputation of the air traffic control system at a time when it is facing severe criticism for long delays to the planned new control centre at Swanwick in Hampshire.
It also comes as fresh doubts have been raised the Government's commitment to controversial plan to partially privatise National Air Traffic Services (NATS). A detailed report into the near miss on 27 August last year found the planes were just three seconds from a collision.
The detailed report by the Air Accident Investigations Branch revealed the near-miss took place after the Virgin plane had missed an attempted landing because of a sudden rain squall and was planning another approach - known as a "go-around" in the industry.
The controller then turned the Virgin plane, which had come from Brussels, right just as the controller in charge of the departing BA jet, which had 95 passengers and crew en route to Copenhagen, directed it on to the same path.
The investigation into the incident blamed a breakdown in communication between two air controllers. The AAIB report found instructions to controllers for handing go-arounds at Heathrow were not sufficiently clear for dealing with potential near misses.
But it added: "When the mentor detected the potential confliction he acted correctly and quickly to advise the two operating controllers." It also concluded NATS placed too great a reliance on "potentially fallible communication" during times of increased workload.
NATS yesterday admitted the near miss had been a "serious incident" and blamed "human error".
But the white-collar union that represents 1,700 controllers and 1,400 engineers working for the NATS, called for greater investment in the system. The Institution of Professionals, Managers and Specialists said the "relentless increases in the volume of air traffic and controllers' workload was eroding the margin for error". The number of take-offs and landings in the UK is rising at about 5 to 6 per cent a year and is approaching capacity.
Angus MacCormick, a national IPMS officer with responsibility for all southern airports including Heathrow, said: "The problem at Heathrow is that there are more planes landing every hour that they have done in the past." He said spacing between aircraft had narrowed while the airport was consistently busy between 5.30am and 11.30pm. The number of air movements recently hit a new high of 1,328 a day.
"There needs to be a recognition of the pressure on air traffic controllers around the country," he said.
He said staff worked for up to two hours and then had a 30 minutes break and called for the working slots to be reduced.
"It is vital when you are working consistently to be able to walk away. We need more staff and that is the problem as the London air traffic centre is understaffed because staff have to be deployed for training at Swanwick," he said. The Guild of Air Traffic Controllers said: "Controllers are under a lot of pressure due to the inexorable increase in air traffic movements."
The Civil Aviation Authority, which owns NATS, said the skies were very busy but insisted the system was the safest in the world and said air traffic controllers' hours were tightly regulated. It said NATS operated at about 80 per cent capacity most of the time, but on occasions that rose to 100 per cent.
But a spokesman said: "I am not aware of any move to reduce the working time and NATS believes that the current regulated hours are adequate."
Any discussion about the air traffic control network inevitably leads to the future of the pounds 350m centre at Swanwick. The question of controllers' heavy workloads has been raised by a number of bodies, including the House of Commons Transport Committee.
In its report, MPs said they were concerned about the increasing pressure placed on controllers, particularly as the opening of Swanwick had been delayed. The new centre will replace the existing centre at West Drayton in west London. It was originally due to open in 1996, but computer software problems have put the opening back to 2000 at the earliest.
The Government announced plans in June partly to privatise NATS involving private investors, including air traffic employees, taking a 51 per cent stake with the Government holding 49 per cent. Swanwick is key to the privatisation as it would give the extra capacity to allow NATS to expand and any delay would deter potential bidders, said to include National Grid.
The Department of Transport yesterday said the Government was still pressing ahead with privatisation, despite reports the project may be dropped before the next election. "It would free NATS from government financial constraints, allow investment to be decided on commercial grounds and provide the right incentives to maximise efficiency," said a spokesman.
But Mr MacCormick of the IPMS claimed these "efficiencies" would inevitably mean worse conditions for his members, that could ultimately lead to a fall in safety.
"The main problem will be that there will be shareholders who want a dividend and the only way they can save money is to reduce the staff or make controllers work longer. It may mean new working conditions and salaries. These are highly relevant to safety because if we are working longer then we are more tired."
However, the DoT spokesman stressed: "Even if Swanwick was up and running it would not have stopped this because it was at Heathrow control tower. This was human error."
The Transport Minister, John Reid, is likely to face tough questions on Swanwick and on safety concerns when he gives evidence to the Commons Transport Committee next week. "Safety is our overriding priority, and the price of safety is constant vigilance," Dr Reid said yesterday.
n The Airport operator BAA, which runs Heathrow, handled 7.1 per cent more passengers in September compared with a year ago, it said yesterday. Stansted achieved 29 per cent growth while Heathrow recorded 5.5 per cent.Reuse content