There are also code sharing arrangements between airlines and railway companies, formally known as air-rail alliances, and commonly marketed as "Rail & Fly" due to the popularity of the Deutsche Bahn codeshare with many airlines.[5] They involve some integration of both types of transport, e.g., in finding the fastest connection and allowing the transfer between plane and train using a single ticket. This allows passengers to book a whole journey at the same time, often for a discounted price compared to separate tickets.