Want to fly from New York to Athens? You might choose Delta or United. But few people know that Emirates — based in Dubai — flies the route.

How about Sao Paulo to Buenos Aires? You might choose LATAM or Aerolineas Argentinas. But you can also hop on board a non-stop flight on Turkish Airlines.

Welcome to the world of the little known secret flights — or in the airline business — fifth freedom flights. These are agreements that allow airlines not based in a country to fly from a city in that country to another city where the airline is also not based.

These are often positioning flights, but it’s legal for you to fly them, and often at a discount.

The latest fifth freedom flight is from Milan to Barcelona on — another airline that may surprise you — Singapore.