After three decades of international flying, jet lag remains the biggest operational and personal challenge for me and all international aircrew. Jet lag’s correct name is Trans-meridian Circadian Dysrhythmia. Trans-meridian refers to the fact that you’ve crossed multiple time zones (meridians). The more you cross, especially eastbound, the worse the effect.

Circadian refers to your body clock, which is normally aligned to a 24-hour rhythm of light, dark, sleep, digestion, hormones, and core temperatures, while dysrhythmia means a disruption or misalignment of that rhythm. Put these together, and it literally means " a disruption of the body’s natural daily rhythm caused by crossing time zones .”

Aviation medicine, sleep specialists, and FAA documents all use similar terminology, a

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