Originally Posted by
giblet
For domestic segments within countries, it is often the best deal as Argentina and Peru have residency restrictions on the lowest fares, and Chile has point-of-sale restrictions on the lowest fares. For international round trips, you may find cheaper (but don't expect deals on one way tix).
On the LAN website, you can book them online - you provide your international reservation #. I believe it costs a bit less if you come in on LAN v. the other OW carriers.