Bureau of Transportation Statistics (BTS) maintains a database of aviation statistics. Customized tables can be easily created, at this BTS link.
To create the graph above, a customized table was created for ‘Domestic Scheduled Passenger Departures Performed’ (see items checked in the query form below). The results illustrate the trend toward fewer air traffic operations at major U.S. commercial airports. There has been a steady decline from the peak in 2004 and 2005. The total departures for 2014 (8,107,594 departures) was 19% below the peak year 2005 (10,035,145 departures).