- If it is by design, the error message should be improved to say that.
- How can you know how many tickets you would sell, if you make impossible to buy them?
Given United tickets from Sweden to places such Las Vegas and Denver seem to be about 300USD more than tickets to Los Angeles and San Franscisco, there is potentially some demand for split tickets. Also some visitors want to go both coasts in one trip. That's us. United open-jaw + Frontier one-way was the best I could find for us.