Another way of increasing capacity at Heathrow would be to build a third runway. The Government ruled out a full-length third runway in the 2003 Air Transport White Paper, in favour of a shorter runway to the north of the existing airport.

In consulting at the time, the Government said the new runway would be used for both landings and take-offs from the outset (mixed mode), with the existing runways operating in segregated mode, as now. 

A third runway would require new terminal facilities north of the A4 and mean that the M4 spur road would be diverted. It would also involve the loss of around 700 properties, but the Grade 1 listed church and tithe barn at Harmondsworth would be preserved. BAA has already put in place schemes to protect the value of properties blighted by a possible third runway. Is your home affected? Find out more about our blight schemes.

Map of third runway area – from masterplan (627KB PDF)

A third runway would theoretically allow the airport to handle up to 720,000 movements a year, half as many again as today. In practice, however, the volume of traffic is likely to be constrained by the need to meet air quality and noise limits.

The economic benefits for the wider economy of a third runway at Heathrow are estimated to be £7 billion a year or £30 billion by 2030.