The Terminal Five proposal by BAA, the privatised owner of three out of four of London's airports - Heathrow, Gatwick and Stansted - is based on a forecast that the capital's airports will need to serve 3.25 million passengers per week by 2016, compared with 1.2 million now. If permission is granted, Heathrow's five terminals would, BAA says, be handling 1.5 million passengers per week, compared with 900,000 now.
BAA is arguing that the fifth terminal, which would cost pounds 900m, is vital to stop Britain missing out on the growth in air travel in the next century.
The terminal would be connected to the Underground system and to the new Heathrow Express shuttle from Paddington. Work on the pounds 300m shuttle, due to be completed in 1997, is being held up by a dispute between British Rail and BAA and by plans for BR privatisation.
A previous application for a fifth terminal at Heathrow lodged by opponents of the Stansted airport expansion was shelved by the Government in 1983, although the planning inspector had reported favourably, because it was concerned at the imbalance between terminal and runway capacity. There was also concern about whether the 600-acre Perry Oaks sludge farm, on the west side of the airport, which is also the site of the present application, could be drained. However, yesterday a BAA spokeswoman said that this presented no problems.
BAA claims that it could build Terminal Five without needing any extra runway capacity and there would less than a 10 per cent increase in the number of flights, currently 7,800 per week, by 2016 because average aircraft size is increasing.
Michael Maine, BAA's group technical director, said: 'If Terminal Five is built, only 1 per cent of flights will be in aircraft of less than 124 seats by the year 2016.' However, he said that if it were not built, more than a third of flights would be in small aircraft because lack of terminal capacity to deal with many more passengers would prevent airlines using bigger planes.
The planning application for the terminal, designed by Richard Rogers, is likely to be called in by the Government next week. A public inquiry will then be held, probably starting in October 1994. BAA expects it will be at least two-and-a-half years before a decision is made. If it is favourable, building could start in 1997.
The first phase, increasing Heathrow's capacity by 200,000 passengers per week, would be completed by 2002. BAA says few jobs will be created but claims that unless the terminal is built, 8,000 existing jobs at the airport would disappear because of new technology and productivity improvements.
Local environmental campaigners are worried that the proposals will lead to increases in flights. Virginia Godfrey, of the Heathrow Association for the Control of Aircraft Noise, said: 'The Government broke earlier promises that the fourth terminal would not lead to increases in the number of flights, but it did.'