Airlines generate additional revenue, known as ancillary revenue, from paid services they offer in addition to airline tickets. These services include checked baggage (especially for low-cost carriers), extra or excess baggage, paid drinks and snacks, in-flight sales, paid Wi-Fi, boarding services such as priority or reserved seating (especially for low-cost carriers), and other options. For some airlines, particularly low-cost carriers, this additional revenue can exceed the base cost of the ticket for some passengers. This phenomenon is also becoming increasingly important for traditional airlines.