Recently I needed to fly from Buenos Aires in Argentina to Sao Paolo in Brazil. Which airline did I choose? LATAM, Aerolineas Argentina? No. It wasn't a South American carrier. Not even a North American carrier. I flew Turkish Airlines. Turkish Airlines? What is Turkish Airlines doing flying between Argentina and Brazil?

Are you wanting to fly from New York to Milan? You could choose Delta, American, or ITA, the Italian carrier. I chose Emirates. And the same question surfaced. What is a Dubai based airline doing flying New York to Italy?

How about Frankfurt to New York? The obvious choices might be Lufthansa or United. Nope. The best alternative: Singapore Airlines.

As you're reading this, somewhere over the Atlantic, a Boeing 777 full of passengers is descending towards Newark. The airline is Emirates. The passengers boarded in Athens. Nobody on the plane has any connection to Dubai.

Flying between Bangkok and Sydney? Thai Airways or Qantas, right? Think again. There's a nonstop flight on Egypt Air.

In most cases, you'll fly on uncrowded flights, get better service and yes, in many cases, lower fares. (My Turkish Airlines flight from Buenos Aires to Sao Paolo — in business class — cost me just $100.

So how did these flights get on the schedule? Are they legal? And how can you find them?

They are what's known as fifth freedom flights, one of aviation's stranger and more useful loopholes, and the reason some of the world's best business class cabins occasionally show up on routes that have nothing to do with their airline's home country.