Southend Airport, one of the six main airports serving London, began life as a landing strip for pleasure flying. The largest flying ground in Essex, it was established by the Royal Flying Corps during the First World War as part of London's air defence network. During the Second World War, the RAF requisitioned the airfield and it served as a Spitfire base during the Battle of Britain and was an important fighter station for the rest of the war. Southend's potential as a gateway to Europe was finally realised with the construction of two runways during the 1950s. During the 1960s, it was one of the busiest airports in the country and home to some of the most innovative aircraft designs of the time. An increase in the length of the runways and in the number of services operated mean that Southend will continue as a gateway to Europe into the twenty-first century.