If you are planning a trip to South America, it is definitely worth considering buying a Mercosur pass. This covers travel in Brazil, Paraguay, Uruguay, Argentina and Chile, excluding Easter Island. It has to be bought as a part of your international ticket and must include travel in at least 2 Mercosur countries. It can be used for a minimum of 7 days and a max of 30 days. It is calculated on the number of miles travelled. The more you travel, the cheaper the fare. You have to travel on certain carriers, but there is a wide range. Ask your travel agent about it.