Who is the AC on the flight schedule? That's who should sign for it. I always defer to rank when haggling over the flight schedule, but it has never happened to me on the jet or in maint control unless I was picking someone (Skipper or XO) up and giving them the courtesy of asking if they want to sign for this leg. 99.9 percent of the time, they say no and take their seat in the back or next to me. Never an issue.