In the States we don't usually bother to call and confirm flights, as we typically receive email updates and such. Not so, on this trip!
Every flight we've taken so far has had an itinerary change.
The Miami-Quito flight changed several times, ending up with an extra night in Miami.
Trying to confirm our Lima to Cuzco flight was complicated because we couldn't reach them at their toll-free number until we used our international phone plan to call their local office. But, good thing we persisted because the flight times had changed.
For our upcoming Lima to Buenos Aires flight on LAN Airlines, we tried to verify our flights online but it wasn't recognizing any of the confirmation or reservation codes we received from AirTreks. AirTreks gave us additional codes but those didn't work either. When we got back to Cuzco, we decided to just go to a LAN Airlines office in person. This is when we discovered that our flight times dramatically changed. Our original 11:45 am flight no longer existed. The only alternative was a 7:10 am flight now. Had we shown up at the airport for the 11:45 am flight, we would've had to have an unexpected overnight stay in Lima or Santiago, Chile.
So, we have learned that flight confirmation is a very important part of our travel plans.