Everyone’s body is so different. I, personally, can go from a day schedule to functioning at full capacity during a night schedule pretty quickly. The late night to early morning swaps during a pairing, on the other hand, are torture. Early morning to late night... not so bad. 117 muddied it up by trying to be overly scientific. Any regs set in accordance with circadian rhythm are like buying a dress shirt off the rack. It’s made to a very narrow viewed version of the “average” person and provides a middle ground, but won’t fit 90% of people perfectly.

I can distinctly remember circa 2007, on reserve at a regional, doing 5-6 legs per day over a 14 hour duty day having gotten maybe 4 hours of sleep the night before. On a regular basis to boot. That was excruciating, even for an early 20s version of me. Change needed to happen, but it needed to incorporate more common sense measures.