I have a really hard time believing it is truly "Illegal." It is clearly a breach of contract in which they have to provide alternate arrangements or a refund, and not very good customer relations, but even with all of the excessive laws in this country it seems like a stretch. Just before I could no longer credit AS flights to DL and just before DL started SEA-GEG flights, so that must have been 5 years ago, which was one of the last times I flew AS, flying SEA to GEG and back. The outbound went MX, so they swapped the Q400 for a 737. Next day, when I returned, the 737 was still sitting in GEG and all of the evening flights had very light loads. I was not happy when I arrived at the airport for my 6pm flight and they told me that my flight and all of the rest of the evening flights (3 or 4) had been CX due to light loads and they were running a special section with the 737 at 11pm. There were 14 people on the flight.