It's actually worse than just 50%.
American
Total Daily Flights: 6,446
Mainline Flights: 3,055 ? 47%
Outsourced Flights: 3,391 ? 53%
Delta
Total Daily Flights: 4,684
Mainline Flights: 2,149 ? 46%
Outsourced Flights: 2,535 ? 54%
United
Total Daily Flights: 5,024
Mainline Daily Flights: 1,735 ? 35%
Outsourced Daily Flights: 3,289 ? 65%
SWA+AT
Total Daily Flights: 3,368
Mainline Flights: 3,368 ? 100%
Outsourced Flights: 0
United States Total Daily Flights: 21,913
Mainline American: 3,055 ? 13.94%
Mainline Delta: 2,149 ? 9.81%
Mainline United: 1,735 ? 7.92%
SWA+AT: 3,368 ? 15.37%
Mainline Outsourced Regionals: 9,215 ? 42%
Others: 2,391 ? 10.9%
http://media.mcclatchydc.com/smedia/2013/06/19/19/52/ePrcN.La.91.jpg