Is it cheaper to fly into one city and out of the same one?

It is often cheaper on paper, but you pay for it in time and bus costs to backtrack across the region. The cost of a multi-city ticket is almost always offset by the savings in bus fares and lost vacation days.

Do I need proof of onward travel?

Yes. Central American immigration officers frequently ask to see a flight reservation leaving the country or the region. Keep a screenshot of your outbound flight handy on your phone.

Booking Multi-City Flights for a Central American Backpacking Trip

Use the 'Multi-City' search tool on flight aggregators to book an 'open-jaw' ticket, flying into one capital and out of another. This saves you from back-tracking across the region and keeps your travel timeline linear.

Map your route first. Decide on your start and end points before opening a browser. Panama City (PTY) and Guatemala City (GUA) are the most common anchors. Trying to book flights mid-trip is significantly more expensive.
Use the Multi-City tool. Avoid 'One-Way' searches. Go to Google Flights or Skyscanner, select 'Multi-City' from the dropdown menu, and enter your arrival city (e.g., San Jose) and your departure city (e.g., Guatemala City) as separate legs.
Set alerts for 3 months out. Central American flight prices fluctuate based on tourism seasons. Track your specific multi-city route for 2 weeks before pulling the trigger to identify a price baseline.
Check regional budget carriers separately. If your itinerary includes a large gap (like getting from Nicaragua to Honduras), check airlines like Volaris or Avianca separately. Sometimes, booking a 'filler' flight locally is cheaper than bundling it into your international ticket.

Is it cheaper to fly into one city and out of the same one?: It is often cheaper on paper, but you pay for it in time and bus costs to backtrack across the region. The cost of a multi-city ticket is almost always offset by the savings in bus fares and lost vacation days.
Do I need proof of onward travel?: Yes. Central American immigration officers frequently ask to see a flight reservation leaving the country or the region. Keep a screenshot of your outbound flight handy on your phone.