Airports of London cannot be expanded due to the docks on either side. It is also the only airport serving London which does not operate at night. A light rail service from London City Airport DLR station, which adjoins the terminal building of London City Airport, links it to the financial district of the City of London at Bank and Monument stations, which offer interchanges with London Underground. Located in the London Borough of Hillingdon, Heathrow is by far the largest of London's airports and considered the main gateway into the United Kingdom for non-European visitors. Heathrow has four terminals and two parallel
London Underground 2009 Stock FICAS technology, giving a thinner bodyshell and hence (along with the larger size) more internal space for passengers. They are the first London Underground trains to be designed since the Rail Vehicle Accessibility Regulations were introduced, so they have more facilities for people with impaired mobility, including multi-purpose areas with tip-up seats and space for wheelchairs and pushchairs, and offset centre door poles for wheelchair access. The trains were the longest deep-level tube trains on the system when introduced, at , longer than the 1967 Stock. The more recently introduced sub-surface S Stock, which is also part of Bombardier's Movia