There are different areas of FAA---There is Part 121 carriers, part 141, Part 61, Part91, etc, etc---maintenance requirements vary between them---for instance---a part 121 operation has specific duty /flight times for crew rest provisions---Kalitta flys freight off someplace far away for $$$$$$, then because crew is out of time(or will be by the time they get to next landing) will fly the a/c as a ferry flight(should be fairy!!!!!) to the next place----they crashed a DC8 in Havana because they were all too tired to function---

Thrust reversers aren't required or used for certifying a/c stopping distances---