Originally Posted by DCBob

First of all, you cannot check in online to an international destination (at the beginning of a trip). When you try to do this, you will not get a BP. Instead, you will get this rather useless document:

"THIS IS NOT A BOARDING PASS. You will need to complete your check-in at an airport kiosk."

At the airport, you have to scan your passport at a kiosk to get a BP. If a visa is required, you will need to go to the check-in counter to see a live person OR your documentation will be checked at the gate before you board.

The reason you can be checked in automatically on your return flight is because your documentation has already been checked. And you probably need to return to your own country!

For domestic flights, you can check in online. That at least gives the airline some comfort that you have indicated within 24 hours of your flight that you intend to board that flight. Of course, there are always some passengers who don't make the flight, but the airline knows it's a very small number that check in and don't board. So the procedure works and it limits the lines at the check-in counter, saving the airline money. Does that make sense?