Originally Posted by BeatNavy

You are correct. PIC and carrier are the approval authority to extend either/both crew members. If the PIC doesn’t concur to an extension for either crewmember, it’s done and over with. Company can’t say anything. No fatigue report required. If Captain concurs, but the FO does not concur because he believes he is not fit to fly, a fatigue report must be filled out. This can be avoided by the captain not concuring in the first place and talking to the FO, hence me getting pssed when I returned from the walk around and my Captain said “hey the company called and asked how you were doing and if I’d agree to extend you, so I did. Hope that’s cool.”