Glossary
Circadian Rhythm
Definition: Circadian rhythm is the body’s natural 24-hour internal clock that regulates sleep-wake cycles, hormone release, and other physiological processes. Long-haul air travel disrupts this rhythm, causing jet lag.
Your circadian rhythm is controlled by a cluster of cells in the brain’s hypothalamus that respond primarily to light cues. When you travel across time zones, these cells need time to adjust to the new light-dark cycle, creating the misalignment that causes jet lag symptoms.
Airlines and travellers employ various strategies to manage circadian disruption. Many business class passengers adjust their sleep schedule before departure, use melatonin to encourage sleep at the destination’s nighttime, and maximise light exposure at strategic times after arrival.
In premium cabins, airlines support circadian adjustment through meal timing (serving dinner when it’s evening at the destination), cabin lighting that simulates day/night cycles, and lie-flat seats that allow sleeping at the appropriate time. Modern aircraft like the 787 and A350 feature LED lighting systems that gradually shift through a spectrum of colours to support natural sleep-wake transitions.