Round-the-world ticket

A round-the-world ticket (also known as round-the-world fare or RTW ticket in short) is a product that enables travelers and tourists to fly and travel around the world for a relatively low price. RTW tickets have existed for some time and in the past were generally offered through marketing agreements between airlines on several continents. Now, they are almost universally offered by airline alliances such as SkyTeam, Star Alliance and Oneworld, or else by specialist travel agencies that will spend time helping customize a trip to the consumer's needs.

They are priced according to class of service, origin of travel, number of continents, mileage (usually between 20,000 and 40,000 miles), and sometimes season of travel. The traveler benefits from the large and optimised network of the airline alliance and can participate in the alliance's frequent flyer programs. However, these tickets are usually subject to restrictions. The start and end of the journey almost always have to be located in the same country and exactly one crossing each of the Atlantic and Pacific must be included in the itinerary. The number of stops is usually restricted to 5-16, and backtracking between continents (especially Europe/Asia) is often restricted. The dates and journey do not have to be pre-planned as travelers can change dates and destinations en route at a local office of any airline in the alliance (although a change of destinations often results in an additional fee, and if the next flight is left open-dated the booking can be dropped by the airlines' computers). Prices vary but are generally in the range of $3000-5000 USD for an economy class ticket.

An alternative for a round-the-world ticket is a continent pass.

Specialist Travel Agencies

It is possible to put together a round-the-world route by combining one-way tickets on various airlines. This is more flexible than restricting yourself to what an alliance offers and, because they discounts on certain long- and short-haul legs, pricing can be competitive. The only practical way to do this — since it requires both knowledge and contacts — is to go to a travel agent who specializes in round-the-world itineraries. These can be found in major cities that are transit hubs — San Francisco, London, New York, Bangkok, etc. — and many of them also provide services online.

The booking process can take a few days or weeks depending on how fast you wish to expedite the process. These agents will get parts of your ticket issued by their contacts in other countries or in-house contracts. This can save a lot of money over the airlines.

From http://en.wikipedia.org/