Mercedes-Benz Citaro
In August 2003 route A40 High Wycombe to Heathrow Airport commenced, initially using second-hand Leyland Olympian double-deckers. By April 2004 these had been replaced by new low-floor Mercedes-Benz Citaro single-deck buses, in a dedicated silver and red livery. The route, which ran in partnership with Buckinghamshire County Council and Heathrow Airport Holdings, was formally introduced in January 2004.