Bargaining unit employees, such as most of us here at UPS, are not considered "at will" employees.
UPS likes to start these draconian policies from time to time instead of actually managing their employees and addressing the problem. Sure, there are always a few employees who just don't want to come to work. Most absences are for legitimate sickness related reasons: either for themselves or a family member. When there is a rash of absences, absent some epidemic, it's more likely a response to abuse or harassment at work. So instead of removing that bad manager or supervisor (or reducing the workload during high-heat times as we are experiencing now and every document you can find including UPS ones say to reduce your activity during midday hours), UPS decides to issue discipline.
When this happens I encourage employees to get on FMLA if they , or a family member, have a legitimate issue and almost everyone does. FMLA will protect your job even better than the Union can and as a bonus it will wreak havoc with managements planning. Management hates FMLA, but they only bring it on themselves.
UPS would be better served by ending these draconian discipline policies and teaching and encouraging their managers and supervisors to actually build a rapport with their employees the way they used to. When you have a management team you enjoy working for, know that they actually care about what is going on in your lives ,and will not add to those problems in life that crop up from time to time; you are much more likely to come to work every day and be more productive.
Of course, doing the above would solve a lot of the problems we have at UPS.