is actually fully booked. Thalys (Paris to Brussels, Amsterdam, and Cologne) services require a compulsory reservation. 2nd class pass holders can travel in Standard class only, 1st class pass holders can travel in either Comfort or Premium class, the latter, while at no extra cost, is on a first-come first-served basis. TGV (France): TGV inOui (French Domestic), TGV Lyria (France ↔ Switzerland), TGV France-Italie (France ↔ Italy), Elipsos (France ↔ Spain) and Alleo (France ↔ Luxembourg and Germany) services require a compulsory reservation. The price of the supplement varies from route to route and can also change depending on availability. Passes aren't valid on SNCF's budget Ouigo services. Trenitalia (Italy): Frecciabianca, Frecciargento, Frecciarossa, first or second class. Reservations are recommended for intercity trains in Italy. AVE (Spain) First and second class. Second-class reservation fees are charged on most other long-distance trains in Spain, such as Arco, Euromed, Alvia, Alaris, and Altaria. ICE train reservations are available. The SJ high-speed train (in Sweden, to Copenhagen) requires a reservation, and booking two months in advance is recommended. Some scenic trains have a panoramic coach, which requires a reservation. Night trains In addition to high-speed trains, many overnight trains require reservations (at extra cost) for sleeping accommodations such as couchettes or sleeping cars; some trains have only sleeper cars. With Interrail's Flexi Global Pass, a direct overnight train leaving before midnight only uses one travel day (the day of departure). Reductions on privately owned trains Although Interrail passes are normally valid only on national railway systems, some private rail systems offer free or discounted service (usually 25 to 50 percent) to Interrail pass holders. Literature Julian Trometer: Europe by Train: Backpacking for Beginners, Berlin 2020, ISBN 979-8695597981. Nicky Gardner: Europe By Rail: The Definitive Guide, Berlin 2022, ISBN 978-3945225035. Marco Polo: Interrail Map + Guide 1:21000000, Stuttgart 2019, ISBN 978-3829739542. Caty Ross & Johan Hausen: European Railway Atlas 2022: Designed for Interrail/Eurail Rail Pass, ISBN 978-1911165484. Timeline 1972: Interrail Pass began, limited to travellers age 21 or younger. It covered 21 countries: Austria, Belgium, Denmark, East Germany, Finland, France, West Germany, Greece, Hungary, Ireland, Italy, Luxembourg, the Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, United Kingdom, and Yugoslavia. The price in the United Kingdom was £27.50 for one month's travel. 1973: UK price increased to £33.00 1976: The age limit for the pass was raised to 23; it was raised again to 26