Jet lag, also called desynchronosis and flight fatigue, is a temporary disorder that causes fatigue, insomnia, and other symptoms as a result of air travel across time zones. It is considered a circadian rhythm sleep disorder, which is a disruption of the internal body clock.

Besides fatigue and insomnia, a jet lag sufferer may experience a number of physical and emotional symptoms including anxiety, constipation, diarrhea, confusion, dehydration, headache, irritability, nausea, sweating, coordination problems, dizziness, and even memory loss. Some individuals report additional symptoms, such as heartbeat irregularities and increased susceptibility to illness.

Children can also suffer the same jet lag symptoms as adults.