What portion of the total amount spent annually on commercial air transportation in the United States eventually goes toward paying for infrastructure, including capital, operational, and security-related costs? Previously unavailable data provided by 10 large carriers are used to estimate the amounts paid through various domestic and international taxes and fees as well as the amounts paid directly by the airlines for airport and air traffic management infrastructure. At least 85% of the survey results can be confirmed through publicly available sources. Combined data sources are used to conclude that in 2004, infrastructure-related costs accounted for approximately 15% of the total amount spent by consumers for passenger and cargo air transport. This would make infrastructure-related costs the third largest category in 2004 (with labor first and fuel second). This conclusion contrasts with conventional wisdom: because of incomplete accounting and data fragmentation, the full magnitude of infrastructure-related costs often is not understood, and these costs are treated as relatively minor.