As the world’s airspace becomes ever more crowded with airliners, the flying actually )becomes safer.

In the United States, the number of air travellers rose from 315 million to 460 million between 1980 and 1987. Across the western World, air traffic is growing at around 20 per cent every year.

So there would seem to be increasing chances of a midair collision – the catastrophe that pilots call ‘the aluminium shower’. But each year, the accident rate goes down. In the USA, there were 1.72 deaths per 100,000 flying hours in 1978; in 1986 there were 0.92. In other words, an aircraft would have to fly 24 hours a day for nearly 12 years before anyone was killed.

Yet the system is showing signs of strain. In 1987, near-misses in the USA occurred at the rate of three a day – double the rate of 1984. On July 8, 1987, for example, two American jumbo jets – both flying towards the USA with a total of almost 600 people on board – missed each other by less than 100ft (30m) over the Atlantic.

The near-miss figures in Europe remain steady, but some experts fear that the American pattern will be repeated in Europe as traffic grows.

The responsibility for ensuring that aeroplanes do not collide in midair falls squarely on the shoulders of the air traffic controllers. And as the flow of aircraft increases, the volume of work becomes constantly greater. In the USA, the Federal Aviation Administration employs about 15,500 air traffic controllers – almost exactly the same number as in 1980.

The main danger points are the airports themselves, for 90 per cent of all collisions and near collisions involving airliners occur as the aircraft climb after takeoff, descend for landing, or circle while awaiting permission to land.