Argentina is a big country, and many of the distances can take days to travel if you don't catch a flight. On the whole, domestic flights within Argentina are quite expensive, but there's a few tips and tricks to book them for less.Argentina is served by two major airlines - Lan Argentina and Aerolineas Argentinas. Whatever the flights, they are almost always cheapest if booked well in advance. On the whole, the flights with Lan are the best value (and the service is much better).
Lan offers an airpass that can be excellent value if you consider taking three or more flights within Argentina, or if you plan on travelling to other destinations served by Lan (eg. Chile or Peru). To use a Lan Airpass, you must have flown to Argentina (or a neighbouring country), with a one world carrier.
Aerolineas also offers an airpass, but it's normally more expensive than standard fares. Instead, a great way to book Aerolineas flights at a discount is to add an extra flight at the end of your flights schedule. By example, if you want to fly Buenos Aires - Bariloche - Buenos Aires, try booking Buenos Aires - Bariloche - Buenos Aires - Montevideo instead. By adding the Montevideo flight (but not actually using it), the flights often cost less. Why? Because the Uruguyuan government subsidises the flights!
See BigTravelWeb.com for more Argentina travel tips, plus tips on travel throughout South America.