London Heathrow Airport (LHR) has long been the busiest airport in the United Kingdom by passenger numbers. Aircraft movements are another metric used, but they are typically used for operational reasons, whereas passenger numbers are more useful in a commercial context. Of course, LHR tops the UK rankings in aircraft, and although the rankings of Europe’s busiest airports have shifted over the past several years, with Istanbul Airport in particular rising rapidly, LHR continues to hold the number one ranking.

London Heathrow Airport is, of course, the primary airport serving London, the capital of the United Kingdom. It is one of the world’s largest and most influential cities, and it’s also one of the world’s biggest business hubs, rivaled only by New York. In addition, London is also tremendously popular with tourists worldwide. As such, it has virtually limitless demand in all corners of the world. London Heathrow Airport is the preferred airfield for overseas visitors and a popular domestic hub for travel within the UK.

The London Metro Area System Of Airports

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London Heathrow Airport serves as the primary hub for UK flag carrier British Airways, and it is the main airport serving the London metropolitan area, which is also served by five additional airports. London Gatwick Airport (LGW) is the city’s second-busiest airport and one of the world’s busiest single-runway airports. In addition to its operations at Heathrow, British Airways also operates a small secondary hub out of Gatwick Airport, primarily serving leisure destinations to complement its business-focused network at Heathrow.

London City Airport (LCY) is located near London’s key financial districts, making it the preferred airport for business travelers. However, LCY is a tiny airport with a single 4,948-foot (1,508-meter) runway and minimal ramp capacity. Furthermore, its location means that there are strict noise-abatement procedures and a steep approach angle. Until recently, the largest aircraft that could serve London City was the Airbus A318-100, although an application has been submitted to permit A320neo operations.

London is also served by Stansted Airport (STN), Luton Airport (LTN), and Southend Airport (SEN). These three airports are all located further from London’s city center, and are primarily used by budget airlines. Although it’s technically called London Southend Airport, SEN is roughly an hour away and is served only by easyJet. Stansted, on the other hand, is the city’s third-busiest airport (ahead of LTN and LCY) and notably has nonstop Emirates flights to Dubai.

Commercial Service To London-Heathrow

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London Heathrow Airport is by far the busiest airport in the United Kingdom, with over 84.4 million passengers passing through its terminals in 2025. This is nearly double the number of passengers that pass through Gatwick, the UK’s second-busiest airport. Manchester Airport (MAN) is the UK’s third-busiest airport and also the country’s busiest airport outside London, with just over 32 million passengers in 2025.

LHR is not just the busiest airport in the UK, but it’s also the busiest in Europe, and the world’s fourth-busiest. LHR also has the world’s second-highest number of international passengers, behind only Dubai International Airport. Heathrow is served by over 80 airlines from around the world and has nonstop service to over 230 destinations in more than 80 countries, making it the world’s most connected airport. In addition, the London metropolitan area airport system is the busiest in the world.

London Heathrow has more daily Airbus A380 flights than any other airport in the world except Dubai, as it’s a hub for prominent A380 operator British Airways and sees significant service from foreign A380 operators. It offers nonstop flights to all six inhabited continents and is also a major cargo hub. Despite its high volume of traffic, Heathrow only has two runways and, by passenger numbers, is the world’s second-busiest two-runway airport, behind only Dubai International Airport. By aircraft movements, however, Heathrow is busier than Dubai.

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The Airline Hubs At London-Heathrow

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British Airways has been headquartered in London since its inception in 1974 (born out of a merger between BOAC, BEA, Cambrian Airways, and Northeast Airlines), with Heathrow as its primary hub. From Heathrow, British Airways operates flights to over 206 destinations in 88 countries with a fleet of over 250 aircraft. It’s a member of the oneworld alliance and one of the founding airlines of IAG (International Airlines Group), along with Iberia.

Virgin Atlantic is the other major airline based in London. Founded in 1984, this carrier also operates its primary hub out of LHR, but unlike Virgin Atlantic, it is significantly smaller and only flies widebody aircraft. The carrier only has 43 aircraft from the Airbus A330, A350, and Boeing 787 families, serving 22 destinations in over a dozen countries, with some routes also originating out of Manchester Airport. Virgin Atlantic is 49% owned by Delta Air Lines and is also a member of SkyTeam.

British Airways operates a joint venture across the Atlantic with American Airlines, IAG members Iberia, Aer Lingus, and LEVEL, along with oneworld member Finnair, meaning that these airlines essentially act as one carrier across the Atlantic. Virgin Atlantic, meanwhile, is part of the SkyTeam transatlantic joint venture that also includes Delta Air Lines, Air France, and KLM. As such, London-Heathrow is dominated by these joint ventures, and as a whole, is a major hub for oneworld and SkyTeam.

The Infrastructure At London-Heathrow

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As previously mentioned, London Heathrow Airport is a two-runway airport, which limits capacity. Heathrow is slot-restricted and one of the most constrained airports in the world. This doesn’t necessarily mean that there’s no space left for more flights, but simply that slots at desirable times are virtually non-existent. With the scarcity of desirable slots and the airport’s “use it or lose it” policy, airlines occasionally trade slots, and prime-time Heathrow slots can sell for up to $75 million.

LHR has four passenger terminals. Terminal Two is LHR’s newest terminal, fitted with 48 gates and home to all Star Alliance carriers flying to Heathrow, along with SAS, Middle East Airlines, Aer Lingus, Eurowings, Icelandair, JetBlue, and Loganair. Terminal Three has 28 gates and is the primary oneworld terminal, but is also used by SkyTeam members Virgin Atlantic, Delta Air Lines, Aeromexico, and China Airlines, along with Emirates, Beijing Capital Airlines, and LATAM.

Terminal Four has 22 gates and is used by all other SkyTeam airlines, along with Malaysia Airlines, Qatar Airways, Royal Air Maroc, Oman Air, and most other non-aligned airlines. Meanwhile, Terminal Five is the primary hub for British Airways (which also operates some flights out of Terminal Three), and is also where Iberia operates all flights out of LHR. The main building at Terminal Five is the largest freestanding building in the United Kingdom, with 53 gates spread across the main terminal and two satellite buildings.

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What The Future Holds For LHR

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London remains as important as ever to the world’s economy, and Heathrow continues to be the preferred airport for travel to the city. But as the world’s busiest two-runway airport (by aircraft movements), there’s little opportunity for growth. This is why the UK government is looking to build a third runway. A plan was previously selected in 2025 by the government to construct another runway parallel to the existing two runways and north of the airfield, which will require the government to demolish part of the M25 highway and replace it with a tunnel under the expansion area.

Although a plan was selected, the final decision as to whether to proceed with this project is still years away. If approved, the project should be fully completed by the 2040s. Heathrow’s third runway faces significant hurdles from nearby residents, who are mainly concerned about added noise levels, as well as environmentalists concerned about the climate impacts from a significant increase in flights at LHR. However, the added capacity would be game-changing given the demand for Heathrow flights.

The plan also includes an expanded Terminal Five and a new satellite building located just south of the new runway. In addition, terminals Two and Three would be demolished in favor of a new Terminal Two that would include three satellite buildings in addition to the main building, while Terminal Four would be largely left as is. In addition to the added capacity for takeoffs and landings, the plan features a significant boost in parking capacity. It’s estimated that, once the expansion is completed, Heathrow will be able to accommodate nearly 150 million passengers.