Actually, Fed Ex carries a lot of the mail for the Postal Service. That started when the Postal Service decided it wasn't going to run its own planes anymore.
Its my personal belief that if the airlines are going to become profitable again they are going to have to start getting more mail and cargo in the bellies of the planes.
And, just within the last month the airlines got some great news on that front. Amtrak is getting out of the cargo business and have indicated its ready to give up its Postal contracts as well.
Amtrak hauls a lot of mail, and now that is mail that is going to have to go on planes as there is already a shortage of truck drivers.
Plus, Amtrak hauled a lot of perishable items like fruits from the West Coast headed to the east coast and time senasitive materials like magazines. That probably going to have to start going by air as well.
Amtraks misfortunes may just be another step for the airlines to return to profitability