The London region is served by six main airports, and a number of smaller ones. There are also some former airports which used to serve London, but have since closed. Some of London's airports (e.g. Heathrow, City Airport, Croydon Airport and Biggin Hill Airport) are or were inside the boundary of Greater London, but others (e.g. Gatwick, Stansted, Southend and Luton) are outside Greater London and Lydd Airport is fully 60 miles from the city centre.