Legendary Airport Story

Heathrow’s Third Runway: Two Decades and Counting

Aerial view of Terminal 3 and the runways at London Heathrow Airport — Heathrow’s existing two runways, already operating near capacity — the reason a third has been under discussion for over two decades. Photo: Panhard — CC BY-SA 3.0

No single runway in commercial aviation has generated more paperwork. Heathrow’s proposed third runway has survived a change of government, a full independent national commission, and a fight that reached the United Kingdom’s highest court — and as of late 2026, it still isn’t built, with Heathrow’s own current estimate pointing toward 2039. The story isn’t one long delay. It’s several real, separate collisions, each one genuinely resetting the clock.

Why Heathrow needs a third runway at all

Heathrow operates two runways, and has done so since well before the airport grew into one of the world’s busiest international hubs. Two runways at that traffic volume leaves essentially no spare capacity — no slack for growth, no resilience against disruption, and a structural ceiling on how many flights the airport can ever handle, regardless of demand. A third runway has been the proposed answer to that ceiling since the early 2000s, and the central argument for it hasn’t fundamentally changed in over twenty years; what has changed, repeatedly, is the politics and law around approving it.

The sequence

The third runway, two decades in

2003

Proposed

The government’s Air Transport White Paper first proposes a third runway at Heathrow as national policy.

January 2009

Approved

Prime Minister Gordon Brown’s Labour government formally approves the runway, targeting roughly 2015 for operation, over strong local and environmental opposition.

May 2010

Scrapped

Labour loses the general election; the incoming Conservative-Liberal Democrat coalition scraps the third runway as part of its coalition agreement.

2012–2015

Re-examined

The independent Airports Commission (the Davies Commission) re-examines UK airport capacity from scratch, ultimately recommending Heathrow expansion over Gatwick in its 2015 final report.

25 October 2016

Re-approved

The government formally endorses the third runway as national policy, based on the Commission’s recommendation.

2018

Parliament

The House of Commons votes to approve the Airports National Policy Statement, the formal planning framework the runway needs.

February 2020

Blocked

The Court of Appeal rules the government’s policy statement unlawful for failing to properly account for the UK’s Paris Agreement climate commitments.

16 December 2020

Cleared

The Supreme Court unanimously overturns the Court of Appeal, ruling the minister had no specific obligation to address the Paris Agreement separately — clearing the legal path, not granting planning permission.

November 2025

Backed

The government formally backs Heathrow Airport Limited’s Northwest Runway scheme.

2026

In progress

A draft Heathrow Expansion National Policy Statement is published and goes through public consultation, with a Parliament vote expected and full planning permission targeted for 2029.

What actually happened in court

The 2020 legal fight is the part of this story that genuinely could have ended the project outright, which is why it’s worth separating from the earlier political back-and-forth. Environmental campaigners, including Friends of the Earth, challenged the 2018 Airports National Policy Statement on the grounds that the government had approved it without properly weighing the UK’s commitments under the Paris Agreement on climate change. In February 2020, the Court of Appeal agreed, ruling the policy statement unlawful on exactly that basis — a genuine, substantive defeat, not a procedural technicality.

The government itself chose not to appeal that ruling. Heathrow Airport Limited, as the commercial party with the most at stake, did, and took the case to the Supreme Court. On 16 December 2020, the UK’s highest court unanimously overturned the Court of Appeal’s decision, finding that the responsible minister had been under no specific legal obligation to address the Paris Agreement separately within that particular policy statement. The ruling cleared the way for the project to proceed through planning — but as Heathrow has been careful to note since, clearing a legal obstacle is a different thing from having an approved, buildable runway.

Why “cleared by the Supreme Court” still isn’t “approved”

Six years on from that ruling, the runway still needs a fresh National Policy Statement to clear Parliament — the 2018 version the Supreme Court revived was itself later superseded by the need for an updated framework reflecting current climate and aviation policy — and Heathrow Airport Limited still needs to secure full planning permission on top of that, which it is currently targeting for 2029. The airport’s own public guidance has shifted the realistic opening date from an earlier 2035 target to around 2039, explicitly describing 2035 as having always been an “ambitious target” that would have required regulatory and policy changes beyond what has actually happened. Given the project’s own history of resets, even that 2039 figure is best read as the current best estimate rather than a fixed date — the only genuinely safe prediction about Heathrow’s third runway, after two decades of evidence, is that the timeline keeps moving.

Sources & Further Reading

Common Questions

Frequently Asked Questions

Has Heathrow’s third runway actually been approved?

The Supreme Court cleared the legal path in December 2020, overturning a Court of Appeal ruling that had blocked it on climate grounds — but a Supreme Court ruling clearing a legal obstacle is not the same as planning permission. As of late 2026, a draft National Policy Statement is still working through consultation and a Parliament vote, and Heathrow itself still needs to secure full planning permission, which it is targeting for 2029.

Why was the runway blocked by the courts in 2020?

The Court of Appeal ruled in February 2020 that the government’s policy statement supporting the runway was unlawful because it failed to properly take the UK’s Paris Agreement climate commitments into account. The government chose not to appeal; Heathrow Airport Limited did, and the Supreme Court unanimously overturned the Court of Appeal that December, ruling the minister had no specific obligation to address the Paris Agreement separately in that policy statement.

When is the runway actually expected to open?

Heathrow’s own current guidance points to around 2039, not the 2035 date floated earlier — the airport has said 2035 was always an "ambitious target" that would have required major regulatory and policy changes to hit. Given the project still needs a Parliament vote on its policy statement and full planning permission, even 2039 should be read as a current estimate, not a locked date.

Why has this taken so much longer than a normal infrastructure project?

Three separate things have each reset the clock at different points: a change of government reversing the previous one’s decision (2010), a multi-year independent commission process to re-examine the whole question from scratch (the Davies Commission, 2012-2015), and a genuine, substantive legal challenge that reached the UK’s highest court (2018-2020). Each was a real, legitimate process, not a procedural delay — which is exactly why the total timeline has stretched past two decades.

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Last reviewed: October 2026. Facts that change, such as fleets, airspace and airline ownership, are re-checked on a schedule. Spotted an error? Email contact@skyplus.news and we’ll fix it. See how we check facts.