BAA has announced an £8.1bn investment programme at London's three main airports.

The ten-year programme, some of which will need planning permission, assumes air traffic will double over the next 20 years.

The programme includes £6.6bn for Heathrow airport in west London, £980m for Gatwick in West Sussex and £600m for Stansted in Essex, where a £60m terminal extension opened yesterday.

BAA's chief executive Mike Hodgkinson said: "The investment is essential if Britain is to have the quality airports it needs."

The plan does not take into account any extra runways that could be built in south-east England. Government options for airport and runway capacity are to be published shortly, to be followed by an aviation White Paper which is expected to contain firm policy.

The BAA plans envisage passenger numbers at Gatwick rising to 42 million using the existing two terminals and one runway.

At Stansted, BAA hopes to invest a further £160m in extending the terminal further to take the airport's capacity to 26.3 million passengers a year by 2012-13 and eventually up to 35 million.

Passenger numbers for the next 11 years are forecast to grow at Heathrow, Gatwick and Stansted from 104.9 million in 2001-2 to 153 million in 2012-13, with 84.7 million passengers using Heathrow by 2012-13. The rise totals 45.8 per cent, and the forecast average annual increase is 3.5 per cent.