A ticket is generally only good on the airline for which it was purchased. However, an airline can endorse the ticket, so that it may be accepted by other airlines, sometimes on a standby basis or with a confirmed seat. Usually the ticket is for a specific flight. It is also possible to purchase an 'open' ticket, which allows travel on any flight between the destinations listed on the ticket. The cost of this is greater than a ticket for a specific flight. Some tickets are refundable. However, the lower cost tickets are usually not refundable and may carry many additional restrictions.