London's six-airport system was not designed as a single network. It emerged over decades as different airfields took on international, leisure, low-cost and business roles.
Before Heathrow
London's civil aviation moved through several sites before Heathrow. Hounslow Heath handled Britain's first scheduled daily international services in 1919; Croydon became London's principal international airport from 1920. Other important former London airfields included Heston and Hendon, while Northolt temporarily handled civil traffic after the Second World War and remains an active RAF station today.
Post-war system
Heathrow opened to civilian traffic in 1946 and became the primary international gateway. Gatwick was redeveloped in the 1950s, while former military sites such as Stansted took on growing civilian roles.
Leisure and low-cost
Luton expanded through charter and package-holiday flying, then became a major low-cost base. Stansted followed a similar low-cost trajectory from the 1990s, while Gatwick mixed leisure traffic with long-haul expansion.
Other airports
London City opened in 1987 in the Royal Docks as a business-focused urban airport. Southend, an older regional airport, re-emerged as a London alternative after redevelopment in the 2010s.
Six-airport system
Heathrow's runway capacity and political limits on expansion helped distribute traffic across multiple airports. The result is not one hub with satellites but six airports with different route networks, airline mixes and ground-transport patterns.