Be forewarned! Make sure their is AT LEAST 2 hrs between your SJO arrival/departure flights and the domestic flight.
I have to eat $400 worth of flights on both arriving and leaving the country because their was only an hour between my incoming and outgoing flights.
They don't tell you this anywhere on there web sites (how about including 1 sentence on your booking form noting this!) and their tickets are non-refundable. And don't even think about asking their customer service to work with you.
And if you're traveling with a Surfboard:
1. they have both length restrictions.
2. NatureAir has a sleazy policy that your board ISN'T GUARANTEED TO TRAVEL ON YOUR FLIGHT, which is ONLY NOTED in their fine print. So if it doesn't you'll have to choose between missing your connecting flight OR leaving your surfboard! Plus the gouge you on the price $40!