http://i151.photobucket.com/albums/s...uskerFrank.jpg
Not any more. Contracts with air carriers. It is my understanding that the USPS uses a variety of contract carriers. It uses belly cargo on most major airlines and has substantial contracts for Domestic carriage with FedEx, some contracts with UPS and international contracts with UPS. There is no longer a dedicated USPS airline. For a time period; shooting from the hip here; I believe Emery had a majority contract and operated 727's in USPS colors.
(As a side note, it is my understanding from my time at passenger carriers that USPS mail was a significant premium and was to be carried even if you needed to bump pax bags. I was told there were fines and future loss of revenue potential if mail didn't make it's scheduled flight. We were told the bump order for weight or bulk was pax bags, pax then mail.)
Essential Air Service may have some runs that carry mail only; however, there are no US government Postal Employees who are full time pilots delivering mail.