In this case, have you tried to consider buying separate tickets by Aerolineas Argentinas/Austral? I think AR/AU has an Argentinian Airpass but they also have attractive domestic fares in Argentina.
http://www.aerolineas.com.ar
Rgs,
Thanks Hardi, from what I read, Aerolineas is really unreliable, but usually cheaper than LAN.
If I can get the discount prices for LAN, a lot of the flights end up being cheaper than Aerolineas, and apparently more reliable.