The most fundamental data to any analysis of the airline industry are traffic, capacity and the relationship of one to the other. Traffic, measured by revenue passenger miles (RPMs), and capacity, measured by available seat miles (ASMs), are together used to determine Average Load Factor (ALF) – the proportion of airline output that is actually sold. In turn, these metrics provide the basis for measures of unit revenue and unit costs. 

Given that other public sources for origin and destination (O&D) traffic are available, this section provides less detail in this area. Like other aggregate data included on this site, traffic and capacity information is taken from airline Form 41 filings with the U.S. Department of Transportation and filings with the Securities and Exchange Commission. An examination of traffic is not complete without an analysis of average fares and revenue.