Is it possible to book mixed-cabin itineraries where one of the segments doesn't have First Class? Looking to book ORD-NRT-BKK and seeing the availability on the American website (ORD-NRT in First, NRT-BKK in Business) but it does not come up on the Alaska website. I can see ORD-NRT in First Class separately, but it doesn't show up when searching both segments together.