Aviation English
Long Haul

What is Biological Clock?

Biological Clock The natural internal time-keeping system that regulates physiological activities, directly affecting crew alertness and fatigue during time zone changes and long-haul operations.

Source: ICAO Doc 9432, FAA PCG

How is “Biological Clock” Used in Practice?

Crew duty times are scheduled in accordance with biological clock considerations to minimize fatigue and optimize alertness.

Certification Exam Relevance

ICAO Level 4ICAO Level 5ICAO Level 6EASA FCL.055

Who Needs to Know This Term?

  • Pilots
  • Air Traffic Controllers
  • Cabin Crew

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Frequently Asked Questions

What is Biological Clock?

The natural internal time-keeping system that regulates physiological activities, directly affecting crew alertness and fatigue during time zone changes and long-haul operations.

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