I must say I was a bit disappointed in the presence of LATAM in S. America. I'm pretty sure they are the biggest airline in S.America based on figures but when I was looking for flights for my recent holiday trip most often other carriers came back with better options.

Partly maybe because the flights I looked for involved touristic rather than business destinations.

AEP - IGR (Iguazu) : Operated by LAN & Aerolinas Argentinas. LAN seems to uses busses to board all it's planes in AEP. Probably cheaper but a bit annoying.
IGR - AEP - SLA (Salta) : 2 times with the bus in AEP. Aerolinas Argentinas had a direct flight between IGR & SLA. Would have been a lot faster.

LPA (La Paz) - EZE : One option would have been with TAM Paraguay but the connection in Paraguay was so bad it would have cost us a day so we decided to go for BoA. Connection in Sucre but a lot faster.

Con for Aerolines Argentinas is their baggage allowance, only 15kg on domestic flights.