Heathrow's third runway reopens the question of domestic air links in the United Kingdom
The planned third runway at London's Heathrow Airport could, if the project passes the remaining political, regulatory and environmental checks, create room for more domestic air links between Britain's largest hub and regional airports. According to the earlier explanation by the British government on domestic connectivity, Heathrow's expansion was conceived not only as a way to increase international capacity, but also as an instrument for connecting the regions with the main British air hub. In that document, the government set out the expectation that around 15 percent of the new slots, meaning take-off and landing times created by the expansion, would be used for domestic flights.
The topic is relevant again because in November 2025 the British government announced that the proposal by Heathrow Airport Limited would be the basis for the continuation of the expansion process. According to the statement by the British Department for Transport, the airport operator is expected to submit the application for development consent for the north-west runway after the review of the Airports National Policy Statement, the key national planning framework for airports. At the same time, Heathrow states that the new runway would be 3500 metres long, that it would enable up to 276,000 additional flights a year and that it would be connected with new terminal and transport works, including the rerouting of part of the M25 motorway.
Regional links were one of the main arguments for expansion
In the British debate on the third runway, the question of domestic routes has a special place because Heathrow has for decades functioned as the most important British air hub for connections to long-haul international flights. When runway capacity is limited, airlines often give priority to more profitable international routes, while some domestic routes are gradually reduced or disappear completely. According to the government's explanation on domestic connectivity, the number of domestic flights to and from Heathrow fell from about 62,000 a year in 1997 to about 40,000, while the number of domestic passengers decreased from 6.7 million to 4.8 million.
The government then stated that without expansion, domestic routes could continue to lose space in favour of international flights. Precisely for that reason, the document stressed that the third runway should enable the strengthening of existing links, an increase in flight frequencies and the opening of new routes to regional airports. Among the potential additional destinations mentioned were Newquay, Liverpool, Belfast International, Durham Tees Valley, Humberside and Prestwick, which would increase the number of domestic routes connected with Heathrow from eight to at least fourteen. According to the government's argumentation, such development would provide better access to international markets for passengers and businesses outside London and the south-east of England.
However, those expectations are not an automatic guarantee that all the announced domestic routes will actually be established. In aviation, this is decided by the commercial interests of carriers, operating costs, aircraft availability, passenger demand and regulatory rules on slots. The British government therefore stated in earlier documents that, if market measures are not sufficient, it may consider mechanisms such as public service obligations for individual routes. Such an approach should ensure that part of the new capacity does not end up exclusively on the most profitable international routes.
What the Heathrow project currently envisages
According to the current information published by Heathrow, the expansion project includes a new north-west runway, additional stands and taxiways, a terminal complex west of Terminal 5, and changes to road and freight infrastructure. The airport states that it is still in the pre-application phase for development consent, in the process used in England for nationally significant infrastructure projects. According to data from the British Planning Data database, the project is registered under the name Expansion of Heathrow Airport (Third Runway), with the reference TR020003, and is currently marked as a project in the phase before formal application.
In its materials, Heathrow claims that the expansion would increase capacity, reduce ticket prices through greater competition and open new routes useful to the whole United Kingdom. The proposal specifically states that the new runway could accommodate aircraft of all sizes, which is important for Heathrow's role as an international hub. The airport also states that it is planning a new public consultation during 2026, meaning that local communities, passengers, carriers, municipalities and other interested parties will again be able to comment on elements of the project before further steps in the process.
The most sensitive construction part of the project concerns the infrastructure around the airport. According to Heathrow, the plan includes rerouting part of the M25 motorway through new tunnels and bridges, while seeking to maintain traffic during the works as much as possible. This part of the plan is important because it increases the complexity of the project, costs and the risk of delays. In its statements, the British government has stressed that the expansion cannot be viewed as blank support, but must satisfy economic, environmental, climate and local conditions.
The government seeks growth, but sets four key tests
British Transport Secretary Heidi Alexander stated in parliament in October 2025 that the government wants a decision on the third runway within the current parliamentary term and that the ambition is to see flights from the new runway in 2035. According to her address, the review of the national planning document should ensure that the increase in capacity is aligned with obligations towards passengers, local communities and the environment. The government named four tests: contribution to economic growth, respect for air quality obligations, compliance with noise obligations, and compliance with legal obligations on climate change, including the target of net zero emissions.
In a later publication by the Department for Transport, it was stated that the independent Climate Change Committee is being asked for an opinion on how Heathrow's expansion should fit into the British emissions reduction framework. This is important because aviation is one of the sectors in which reducing emissions is particularly difficult, and increasing airport capacity can create additional demand for flights. At the same time, the government said that the project would have to be privately financed and that taxpayers should not bear the cost of building the third runway and related infrastructure.
The Department for Transport also highlighted the modernisation of airspace above London and the wider United Kingdom area. According to the government publication, London airspace, which records more than 1.1 million take-offs and landings a year, must be redesigned so that it is ready for a larger number of operations if the third runway is built. This means that the debate on domestic routes does not come down only to the construction of a concrete runway, but includes the wider system of air traffic control, noise protection, slots, airport access and competition among carriers.
The regulator is considering how to limit costs and protect passengers
The Civil Aviation Authority, the British civil aviation regulator, opened a consultation in May 2026 on a shortlist of regulatory models that could be applied to Heathrow's expansion. According to the CAA's announcement, the aim is to assess which model would best protect consumer interests and ensure the efficient, timely and cost-responsible delivery of additional capacity. The regulator stated that the consultation follows on from a working paper from November 2025, which considered whether a different expansion model could better serve passengers and airport users.
That discussion is particularly important for domestic routes because Heathrow's high costs can directly affect the viability of shorter routes. If charges for airlines and passengers rise sharply, regional links could become harder to sustain, even if physical capacity is available. The regulator is therefore considering not only the technical construction model, but also the way in which the costs of early works, planning and future infrastructure can be passed on to users. In a separate announcement, the CAA said that it would publish the final decision on the regulatory treatment of early expansion costs during the summer of 2026.
The discussion includes Heathrow, airlines and alternative promoters. According to reports in the British media, some airlines and industry actors support an alternative, phased proposal by the Arora Group, which, according to them, could reduce costs and avoid some of the most difficult works on the M25 motorway in the initial phase. The government, however, in November 2025 chose Heathrow Airport Limited's proposal as the basis for the continuation of the official process. That does not mean that the project has already received final permission, but that, on that basis, the review of the planning framework and the preparation of the development consent process will continue.
Why domestic routes depend on more than the runway itself
Although the third runway can create physical room for more take-offs and landings, domestic connectivity will depend on political decisions and market incentives. Heathrow previously announced discounts for domestic passengers and a route development fund, which the British government cited as one of the tools for encouraging regional links. However, such incentives have limited reach if carriers judge that international routes are more profitable for them or if regional airports do not have sufficiently stable demand for daily links with London.
Domestic routes to Heathrow have a different logic from direct flights to tourist destinations. Their main value is often in connections to long-haul flights to North America, Asia, the Middle East or other global markets. For business passengers and regions that do not have a large number of direct international links, access to Heathrow can mean faster travel and better connectivity with export markets. On the other hand, for some routes the railway can be more competitive, especially where land connections are faster, more reliable and less exposed to airport security procedures.
That is why the British debate increasingly speaks of a combination of measures. One is the construction of an additional runway, the second is legal protection for part of the slots, the third consists of financial incentives, and the fourth is the modernisation of airspace and airport access. If these measures are not coordinated, the increased capacity could primarily end up on international routes with higher yield per passenger. If they are coordinated, Heathrow could again have a broader domestic network and thereby strengthen its role as a national, and not only London, air hub.
Opponents warn of noise, emissions and the impact on local communities
Heathrow's expansion has for years provoked strong opposition from local authorities, residents and environmental organisations. The London Borough of Richmond upon Thames, for example, in recent publications again confirmed its opposition to the third runway and measures that would increase the number of flights, noise, air pollution or health risks for residents. Similar criticisms in the British public debate relate to greenhouse gas emissions, demolition or changes in settlements near the airport, increased road traffic and prolonged construction works.
Government documents acknowledge that the expansion must meet legal and environmental obligations, but critics argue that it is difficult to reconcile strong growth in air traffic with climate policy goals. In this part, an important role will be played by the opinion of the Climate Change Committee, environmental impact assessments and public consultations within the development consent process. Heathrow, on the other hand, claims that the expansion will bring economic benefits, new jobs and better connectivity, along with measures to mitigate the impact on local communities.
For passengers and regional airports, the key issue is that the continuation of the process should make clearer whether promises on domestic links will be translated into enforceable rules. It is currently confirmed that the third runway project is once again at the centre of British infrastructure policy, that the government wants a decision during this parliamentary term and that the regulator is considering models that should limit costs. But it has not been officially confirmed which additional domestic routes would actually be opened, which carriers would operate them, how frequently they would fly and under what commercial conditions.
Next steps in the process
According to announcements by the government and Heathrow, 2026 is a key year for the political and planning framework of the project. The government is reviewing the Airports National Policy Statement, Heathrow is announcing a new public consultation, and the Civil Aviation Authority is considering regulatory models for financing and managing the expansion. Only after these steps is a fuller application for development consent expected, in which the technical works, impact assessments, transport solutions, compensation measures and financing method would have to be presented in detail.
If the project progresses towards the government's target, the new runway could be operational in 2035. Until then, the debate will continue on whether increased international capacity, more accessible domestic links, acceptable costs for passengers and carriers, and respect for environmental obligations can be achieved at the same time. For regional airports, the most important question remains whether domestic connectivity will be protected by concrete rules or will depend on a market that has so far often given priority to the most profitable international routes.
Sources:
- GOV.UK, Department for Transport – explanation on Heathrow's north-west runway and domestic air connectivity (link)
- GOV.UK, Department for Transport – announcement that Heathrow Airport Limited's proposal will be the basis for continuing the expansion (link)
- GOV.UK, Department for Transport – parliamentary statement by Transport Secretary Heidi Alexander on the review of the Airports National Policy Statement (link)
- Heathrow Airport Limited – current description of the third runway proposal, terminal works and next steps (link)
- UK Civil Aviation Authority – consultation on regulatory models for the expansion of Heathrow capacity (link)
- Planning Data, Ministry of Housing, Communities and Local Government – status of the Expansion of Heathrow Airport (Third Runway) project in the infrastructure projects database (link)