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.

U.K. Treasury chief Rachel Reeves says that the new Labour government is backing the construction of third runway at London’s Heathrow Airport

A map, created for a 2019 public consultation, shows how the airport could be laid out post-expansion. The third runway, labelled as ‘1’, would sit north-west of Heathrow’s current infrastructure, towards Colnbrook and Harmondsworth.