FedEx is well on their way towards that number. FedEx was a good place to work at one time. That reputation is what kept employees from quitting. That is not the case anymore and will be Amazon 2.0 when it comes to turnover.
In a market that is becoming fiercely competitive the quality of employment is often the first to suffer and suffer the most. Granted, to survive as a blue collar worker in such a tough environment undergoing change at a blurring rate it requires a strong work ethic .Trouble with that is that many employers who enjoy the benefit of having exceptionally productive workers are also among the greediest employers and continue to demand ever more production until the disparity between the value demanded and the value offered becomes too extreme. The result is that the best people up and quit and often with no prior notice.
In the past young, healthy, productive and dependable blue collar workers with intellects strong enough to learn quickly weren't that hard to find. Due in part to the huge WWII boomer population.
That's all changed now, especially with boomers either retired or shoved out and much lower birth rates.
The carriers who survive will be the ones who can most quickly and completely adapt to the changing face of the American workforce. especially in the box and parcel business that at least for the foreseeable future will continue to need mountains of hand labor.