Predictability is key. We do hub turns and they are relatively predictable. I have to plan sleep and exercise a little bit, but it’s not bad. For one of our customers, our company consistently builds lines where pilots fly during the day one day, all night the next, the day after, back to nights, etc. Those are a little worse, but also still manageable since you can still anticipate things.
When schedules change every couple hours planning rest and exercise becomes very difficult.