London's airports

Every London airport is developing options to increase capacity. The Mayor is clear that airports must show that any such plans will not cause significant environmental harm or place undue pressure on transport networks. It is essential that local communities and Londoners in general do not suffer increased noise or air pollution emissions or worsening congestion as a result of an airport's plans.

The Mayor and TfL are in regular contact with London's airports and are keeping abreast of their plans.

Heathrow expansion

The proposals for Heathrow expansion raise significant concerns about the impact on the environment and transport. The Mayor, together with local authorities and environment groups, brought a legal challenge against the Government's Airports National Policy Statement (NPS) enabling a third runway at Heathrow.

On 27 February 2020, the Court of Appeal determined that the NPS was illegal on climate change grounds and suspended the NPS with immediate effect. The Mayor welcomed the ruling and is seeking to ensure that expansion does not go any further.

The Government first announced in October 2016 that it would support a third runway at Heathrow Airport. Between February and May 2017 the Government held a public consultation on its draft NPS, followed by a second consultation in autumn 2017.

In April 2018, the Government published "Beyond the horizon" which supported other UK airports making best use of their existing capacity.

The Secretary of State formally designated the NPS on 26 June 2018. This prompted the Mayor to launch a legal challenge of the NPS.

Heathrow decided to proceed with its expansion plans, in preparation for submission of a Development Consent Order (DCO) application. It published an initial consultation in January 2018, followed by a consultation in January 2019 on airspace and runway operations. In June 2019, it published its statutory DCO consultation.

Following the Court of Appeal ruling, Heathrow has suspended its DCO preparation.

Response to the Heathrow NPS and DCO

The Mayor has made submissions to both of the Department for Transport's (DfT's) consultations on the draft NPS. In his responses, the Mayor set out his serious concerns about the impact of a third runway at Heathrow on road and rail networks, air quality and noise.

He has also responded to calls for evidence on the NPS by the House of Commons Transport Select Committee in April 2017 and again in December 2017. A further submission was provided to clarify points raised by the DfT and Heathrow Airport Limited (HAL) during the Transport Select Committee hearings.

Submissions have also been made by the Mayor and his team to the Heathrow DCO consultations to date.

The Mayor's NPS responses and a review of the final NPS - along with other submissions to Government and HAL consultations - are on the Aviation page in Publications & reports.

Heathrow expansion effects

As part of our NPS response we did detailed analysis and modelling to understand how the expansion of Heathrow would affect road and rail access, air quality and noise. The serious issues raised as part of the NPS response have not been addressed by Heathrow in its DCO process.

Road and rail access

An expanded Heathrow Airport would mean an additional 170,000 trips by passengers and staff each day. The Government has suggested that Heathrow can expand without resulting in any extra road trips to and from the airport. For this to happen with a third runway, the percentage of people using public transport to get there would need to increase from 39% to 65%.

Our analysis indicates that this cannot happen without extra connectivity and capacity on the rail networks serving the airport. The Government's proposals do not currently guarantee the significant investment needed to create this, nor does Heathrow accept the need.

Air quality

Heathrow is one of the worst air pollution hotspots in London and legal limits for air quality are already exceeded in the surrounding area. Even without expansion bringing more flights and more journeys to and from the airport, there is a huge challenge to clean up the air.

Our analysis indicates that a bigger airport will make air pollution worse and neither the Government nor Heathrow have been able to show how legal limits for clean air can be met once a third runway is operating.


Unacceptable noise from the airport already affects far too many people - not just those in the immediate vicinity but also those who live under the flight paths across London and in neighbouring areas.

Our analysis indicates that at least 200,000 more people will be exposed to unacceptable levels of noise.


Neither Government nor Heathrow has shown how a third runway can operate without a material impact on the ability of the UK to stay within its carbon targets and budgets.