Originally Posted by gloopy

Obviously there is no possible way to stay completely within one's circadian cycle doing international. That's why its augmented to mitigate that inevitable concern.

Circadian flipping domestic, however, is done for flexibility, staffing and cost and yes to some extent flight crew demand. 117 (unaugmented domestic) does not adequately protect that from a human physiology point of view. That freight train is long, heavy, fast and the amount of track required to stop and turn it around goes far past the horizon.