Because they're trying to keep you on reserve without actually putting you back on reserve, considering it would be illegal to do so once you've already started a FDP. The only way you could be put back on reserve after starting a FDP is after a 10 hour rest/8 hour sleep opportunity. That's pretty cut and dry to me.

My last airline did this same exact thing, and we were specifically told by our FSDO, we had no obligation to answer the phone if called in this scenario. In that FSDO's interpretation, if you were not notified of more flying added onto your schedule either in the air during your last leg, or after you'd blocked in + 15 minutes, you were done. UNLESS you chose to answer their call later that day, and had FDP left, you had to do it.

And there is no discrimination of who these regs apply too... You say "reserves beware." This scenario happens to line holders too. Reserve, lineholder, captain, FO, black, white, orange, this applies the same to everyone. You aren't on reserve, you're on remaining FDP. It's a tactic to TRY and keep you on the hook by scheduling, but unless you're on a regular or airport reserve shift, you're not required to be available. However, if you answer the phone with FDP left... Whelp, saddle up and go back to work.

It's definitely frustrating that each company apparently interprets federal regulations differently. Shouldn't be that way. If Mesa is somehow interpreting this differently than other airlines and a FSDO that'd be good to know. Thanks for the help.