One point about extensions that I think is a big oversight on 117. If the science says that you would typically be fatigued when the clock strikes XX hours what makes us a better judge of that? Yes we are the only ones that can make that decision when it comes to extension but the rules are there not only to protect you from the company but also from yourself.

This flight was roughly 2.5-3 hrs which means if you are just about to push you are making a decision on whether or not you will be fatigued in three hours. How can a human being make a decision on how they may feel that far into the future unless you are fatigued at that minute. While on the approach into Dfw is too late to come to the realization that you are fatigued.

Prior to 117 when many airlines had a non punitive fatigue policy already in place many pilots did not call in fatigued when they should have. Why? Because when you are fatigued you are not a sound decision maker and have a hard time actually judging your own fatigue.

So IMO never extend. The science says you shouldn't but the airline lobby got extensions put in to the final 117 rules because money talkes and pilitians are crooked.