There is an extensive network of domestic flights, with refreshingly low price tags, especially in the Andean countries (Bolivia, Ecuador and Peru). After 18-hour bus rides across mountainous terrain on atrocious roads, you may decide to take the occasional flight.
There are drawbacks to flying, however. Airports are often far from city centers, and public buses don't run all the time, so you may end up spending a bit on taxis (it's usually easier to find a cheap taxi to an airport than from one). Airport taxes also add to the cost of tickets; they are always higher for international departures. If safety concerns you, check out the 'Fatal Events by Airline' feature at www.airsafe.com.
Avoid scheduling a domestic flight with a close connection for an international flight or vice versa. Reconfirm all flights 48 hours before departure and allow ample extra time at the airport.
Air passes offer a number of flights within a country or region, for a specified period, at a fixed total price. Passes are an economical way to cover long distances in limited time, but they have shortcomings. Some are irritatingly inflexible: once you start using the pass, you're locked into a schedule and you can't change it without paying a penalty. The validity period can be restrictive and some passes require that you enter the country on an international flight – you can't travel overland to the country and then start flying around with an air pass. Citizens of some countries are not eligible for certain air passes.
A few South America air passes exist and can save you a bit of money, provided you can deal with a fixed itinerary. These mileage-based passes allow travelers to fly between cities in a limited set of countries. The restrictions vary, but flights must be completed within a period ranging from 30 days to 12 months. You'll pay higher rates (or be ineligible) if you arrive in South America on a carrier other than the one sponsoring the air pass.
Gol South America Airpass (www.voegol.com.br) Includes Brazil, Argentina, Bolivia, Chile, Paraguay and Uruguay.
One World Alliance Visit South America Airpass (www.oneworld.com) Includes Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay and Venezuela.
LATAM South American Airpass One of the most extensive networks around the continent; covers some 124 different destinations in Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay and Venezuela.
Most air passes are only good within one country and are usually purchased in combination with a round-trip ticket to that country. In addition, most air passes must be purchased outside the destination country; check with a travel agent. Argentina, Brazil and Chile all offer domestic air passes.