BACKGROUND: Sleep and fatigue management is one of the main challenges in airline operations scheduling. Our aim was to compare the differences regarding fatigue, sleep, and labor specificities between the two most common types of flight, short/medium haul (SM-H) and long haul (L-H), in a large sample of airline pilots.METHODS: A self-report questionnaire was developed, composed of socio-economic and labor questions, and psychological assessment scales for fatigue and sleep. Associations of these variables and type of flight were tested.RESULTS: Of the total sample of Portuguese airline pilots (N = 435), 313 (72%) were from SM-H and 122 (28%) were from L-H. For SM-H, the values obtained for sleep complaints were 34.2%, daytime sleepiness 61.6%, and fatigue 93.0%. For L-H, 36.9%, 53.3%, and 84.4%, respectively. Looking at labor variables, the differences between the two types of flights were evident, with SM-H pilots’ having statistically significant higher mean values of duty and flight hours, numbers of sectors, and early mornings. Only the mean number of night periods was higher in L-H pilots. All values were reported for 28 consecutive scheduling days.CONCLUSION: Night periods and time-zone crossing may explain higher prevalence levels of sleep disturbances in L-H pilots. However, the values for daytime sleepiness were higher in SM-H pilots, which may be attributed to diminished sleep caused by a combination of frequent early starts and long duty periods. Taking into account the large differences between the two types of flights, different regulatory limits should be considered by aviation authorities.Reis C, Mestre C, Canhão H, Gradwell D, Paiva T. Sleep and fatigue differences in the two most common types of commercial flight operations. Aerosp Med Hum Perform. 2016; 87(9):811–815.