One of the challenges with the federally regulated industries that are subject to both part I and part III of the code is that it's quite unusual, actually, particularly in the transportation industry, for employees to be paid on a standard hourly wage or a salary model. Instead, you often have very complex systems of credits and non-time-based compensation schemes that determine how much someone is paid.
Flight attendants present a great example. Flight attendants are not paid solely based on time. They're paid based on a very complicated system of credits and guarantees that apply to their compensation.