Source: U.S. Bureau of Transportation Statistics  

Release: Transportation Services Index and Seasonally-Adjusted Transportation Data  

Units:  Thousands, Seasonally Adjusted

Frequency:  Monthly

Notes:

Data from all U.S. air carrier domestic, scheduled passenger flights.

This data is collected by the U.S. Department of Transportation, Bureau of Transportation Statistics (BTS) calculation from BTS U.S. Air Carrier Traffic Statistics reported in BTS' monthly Air Traffic Data release, available here.