As airlines take delivery of their new long haul aircraft they often put them into service on domestic routes on train pilots and crew. Americans fleet of 787-800s is slowly growing and in the new year you will have the opportunity to try one of them out between Dallas and Chicago before it goes into international service.
Flight times vary between January and March but it seems to be flying almost every day. If you happen to be traveling between the cities this is definitely the way to do it as the planes will be brand new and much more enjoyable than a 737.
These flights will have the international seat configurations so paying the extra for first/premium economy or using miles is definitely recommended.
The route is currently available for 15,000 Avios or 25,000 AA saver points if you want to use miles and travel up the front.