Plans to expand London's other airports are already further along than Heathrow's and have in the past been viewed as an alternative to a third Heathrow runway. Work is set to start this year to expand capacity at Stansted's terminal. The government is due to make a decision on Gatwick airport by 27 February.

Heathrow third runway location – map reveals new area airport will cover - Part of the M25 could be rerouted through a new tunnel to make space for the runway