1. Particularly for newer airlines, route maps may change with some frequency. Keep tabs on new routes and changes on each airline's Web site.
2. For those discounters that do not issue seat assignments, expect a slightly less orderly "line" at the gate than you might find in the U.S., on Southwest for example. The European character's less stringent premium on personal space can create something more akin to a soccer mob crush than a proper "queue."
3. As in the U.S., many international discounters fly to and from small alternate airports. If you are not familiar with overseas airport codes and names, do your homework so your connections, lodgings, and transport to and from the airport go smoothly.
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4. Especially at larger airports, discounters can sometimes host gates located in nooks and crannies of the airport. If you are flying into a large airport on a major airline to connect to a discounter flight, check out the airport map to get a sense of how far it might be to your gate, and how to get there using airport transport systems (monorail, buses, etc).
5. Not all discount airlines are shoestring operations; Ryanair is said to be one of the world's most profitable airlines at present. However, you should be aware of the financial condition of your chosen airline when purchasing tickets, especially in the fast-growing Asian market, where a shakeout is predicted by many analysts.
6. Very few discounters have baggage agreements with major carriers, so if you are making a connection to or from another airline, you may have to collect your bags at the luggage carousel, and then recheck them for your next flight.
7. Additionally, luggage restrictions may vary on discount airlines; short-haul carriers tend not to accommodate larger items -- and many discounters now charge fees to check any luggage at all.
8. No-frills often means exactly that -- expect to pay extra for food and even water in flight.
U.S. Discount Airlines
9. Most international discounters (and many domestic discounters as well) sell on a first-come, first-served basis, with the lowest fares selling first.
10. While the European rail system is favored by many European visitors, don't assume that the train is always going to be cheaper; many international discount airlines offer astoundingly low fares, such as Ryanair's frequent 2 GBP fare sales. For a head-to-head comparison, see Europe -- By Plane or By Train?
11. U.S. discounters sometimes fail to appear on the major booking sites, and this is even more true of international discounters, particularly in Asia. The only way to find and purchase many of these fares will be by monitoring the airline Web site.
Several sites allow you to search multiple discount airlines simultaneously; here are a few of the best and most popular: