I think there has been a major refocus on the bottom line vs reliability at UPS.
I remember in 1987, I was flying an Aero Commander 500 out of Scottsbluff, NE for Corporate Air on a UPS subcontract. I broke one day and UPS flew a Lear in to take my 50 boxes to SDF to make the sort and not lose service. Nowadays, that would be laughable as it costs way to much (which I actually think is prudent). UPS will just tell the customer, "sorry, the plane broke, you don't have to pay for it" (and that's best case scenario).
It never made an sense from an economic standpoint to run the Lear launches. UPS just had "getting the boxes there" as a higher priority than "making money". I don't believe that to be the case, anymore.
So, to answer your question, I think there is very little, to no, "short call Lear charter ops", like the old days. We still have a huge feeder operation and I don't see that going away.
The Lear lauch was never about a lack of lift. It was about irregular ops and the overriding feeling UPS had that getting that box there was worth any price. They just don't look at it that way anymore.