Missoni E, Nikolić N, Missoni I. Civil aviation rules on crew flight time, flight duty, and rest: comparison of 10 ICAO member states. Aviat Space Environ Med 2009; 80:135–8. Introduction: Members of the International Civil Aviation Organization (ICAO) use various criteria to control flight crew scheduling and rest periods with the intention of reducing fatigue and thus improving airline safety. Comparison of these rules across nations may allow future harmonization of the criteria. Methods: The regulations of 10 ICAO member states were compiled to determine the factors used by each to control scheduling. Results: We identified 12 factors that are used by member states in their regulations; specific nations use 4–7 of these factors. The most frequently used criteria and the number of states using them include Duty Time (N = 8), Crew Augmentation (N = 8), Night Flight (N = 7), Number of Flight Segments (pairs of takeoffs and landings—T/L) (N = 6), Flight Range (N = 6), Flight Time (N = 5), and Number of Crew (N = 5). All 10 states have established limits on Flight Time and/or Duty Time, and 6 have requirements related to Previous Rest and/or Night Sleep. Seven member states undertake regulation of Night Flying, but they vary in defining “night” and the maximum permissible duration of night duty. All states limit flying hours on a monthly and yearly basis, but the specified limits vary. Discussion: Although the 10 states in this study have common aims and premises for regulating crew duty, their regulations diverge with respect to details, using different tools in an effort to prevent the occurrence of excessive fatigue in aircrew members.