[sneeze-slayer]

Crew fatigue is an ATC concern insofar as it contributes greatly to accidents. The controllers may have volume goals, but the ultimate goal is safety.

[nradov]

Crew fatigue really isn't an ATC concern. The FAA and airlines set rules for crew fatigue management. Flight plans are designed to keep the crew within limits even if they have a delay or diversion. It is simply not a controller's job to assess a flight crew's fatigue state, or second guess whether they need an alternate plan due to fatigue. Controllers aren't trained or qualified to do that.