I just spoke with my friend at Ameriflight. After about three years you can enter the 'mentor' program which will get you an interview with UPS. It is not a 'flow' but rather a 'preferred hire'. One way is to get on as a Brazilia FO (which seems to have a lot people applying nowadays). The other is get on as a Navajo Chieftain captain, but the AMF Chieftains will be going away at the end of the year.