Book excerpt: The potential for fatigue to negatively affect human performance is well established. Concern about this potential in the aviation context extends back decades, with both airlines and pilots agreeing that fatigue is a safety concern. A more recent consideration is whether and how pilot commuting, conducted in a pilot's off-duty time, may affect fatigue. The National Academy of Sciences was asked to review available information related to the prevalence and characteristics of pilot commuting; sleep, fatigue, and circadian rhythms; airline and regulatory oversight policies; and pilot and airline practices. This interim report summarizes the committee's review to date of the available information. The final report will present a final review, along with the committee's conclusions and recommendations based on the information available during its deliberations.