okc465:
How do you provide overnight parcel service if you don't fly at night?
They know when they sign the hiring papers. The pay is very good and the industry is not nearly as volatile as the pax carriers.
Plus, when they get senior there are some day flights that haul second and third day packages.
Some of them adapt to flying on the back side of the clock, some don't do so well. Those who don't commute tend to do a lot better. But, that's true for the entire industry.
As far as their international package flights go, they are no worse than U.S. pax international flights.