Is it cheaper to buy separate tickets?

Rarely. While a budget airline might show a lower price for one leg, the lack of connection protection means if a flight is delayed, you lose the value of the next ticket entirely.

What happens if I miss a connection?

If all flights are on one ticket, the airline must rebook you. If you booked separate 'self-transfer' tickets, the second airline has zero obligation to help you.

Booking Multi-City Flights Across South America

Use the 'Multi-city' search tool on a global distribution system like Google Flights rather than booking individual legs separately. This bundles your itinerary under a single booking reference, which is critical for protection if one connection is delayed or cancelled.

Map your 'Open Jaw' route. Don't try to backtrack. Plan your route in a logical loop or straight line (e.g., Lima to Cusco to Buenos Aires to Santiago). Use a tool like ITA Matrix or Google Flights to test your route before purchasing.
Use the Multi-City search engine. On Google Flights, toggle from 'Round Trip' to 'Multi-city'. Add each flight leg one by one. This forces the airline to calculate the ticket as a single fare class.
Verify carrier alliances. Look for flights operated by partners within the same alliance (e.g., LATAM with Delta/SkyTeam or Avianca with Star Alliance). If your flights are on the same PNR (Passenger Name Record), the airline is responsible for rebooking you if you miss a connection due to a delay on a previous leg.
Check baggage interlining. Confirm if your bags will be checked through to your final destination. Even on multi-city tickets, some smaller regional carriers in South America require you to collect and re-check bags at transit hubs like Lima (LIM) or Bogota (BOG).

Is it cheaper to buy separate tickets?: Rarely. While a budget airline might show a lower price for one leg, the lack of connection protection means if a flight is delayed, you lose the value of the next ticket entirely.
What happens if I miss a connection?: If all flights are on one ticket, the airline must rebook you. If you booked separate 'self-transfer' tickets, the second airline has zero obligation to help you.