Air Force One often lands at Stansted Airport during visits to the UK for several reasons related to security, logistics, and convenience. Stansted is a major international airport near London that can accommodate the large Boeing VC-25A aircraft used as Air Force One. It also allows enhanced security measures and easy coordination with British authorities, including a large Secret Service presence and local police support. The airport provides a secure staging area for the president's entourage, motorcade, and support vehicles like "The Beast" (the presidential limousine). Additionally, depending on the visit, Air Force One's landing at Stansted facilitates easier onward travel to key locations such as Windsor Castle, where royal ceremonies and state events take place. This airport choice helps manage protests and keep the visit secure and efficient away from central London congestion.

In summary, Air Force One lands at Stansted primarily for security, logistical efficiency for state visit events, and its capacity to handle the presidential aircraft along with associated security infrastructure.