Well all that is so complex that I just wonder who actually polices those scheduling rules...Seems to me that if all the rules are obeyed by the schedulers then there should be no problem :)

That is the idea, they make it complex enough that it seems hard to understand some parts it, so only the upper level officials or the higher paid airline lawyers can play around with it.

While trying to refuse arguments of a foreign aviation regulatory agency that wanted to change their national FDTL limitations because an airline wanted to do transcontinental flights, and as you can correctly guess that airline was pushing to their favor including pilots flying 14 continuous hours without rest bunks and turn around after an 8 hour rest at a nearby hotel, I browsed through some countries ruling, and found different ways to look at FDTL. That information helped to prepare a good answer to the proposed change, and you are right, nobody at the airline headquarters and the authorities like me anymore.

But a strong mesage to everyone was posted:
Safety is number one in the flight line. Tired pilots are dangerous.

Well keep up the good work...Seems to me that a computer program is required called "FDTL"...The program would have every rule in it and the user input would be a pilot's scheduled roster...The output would be the various reject points with the name of the rule that the point was contravening.

Actually, there is a program called SAFE which deals the subject of air crew fatigue, that was developed using various data from actual flight crews doing flights in different real scenarios, being short routes to ultralong ones. The model is in use by some airlines now.

In reference to the Part 121 requirements I was rather interested the other day as a pax on a late afternoon flight departing Houston when the Capt announced that he was on his 13 hour on push back (2 crew) with expected delays.

We then sat in a without moving in a line for 45 mins when sanity was regained when he announced that they were out of hours and would be returning to the gate. The question being what are the hours for two crew?

Two crew, that is a Capt and FO in the US, flying domestic are maximun of 8 hours flight time and max. 16 hours on duty. The 8 hours of flight can and is sometimes exceeded when the delay is not the fault of the air carrier. IE: mx. wx, etc.

You can not be scheduled for over 8 hours though. The max 16 hour duty day can not be exceeded. That is, if you are taxiing out and your T/O is delayed for whatever reason, you must calculate your reasonable estimate new time of departure. If this new time of departure will cause you to land at destination with over 16 hours, that is ETA plus normaly 30 minutes for post flight and close the aircraft, then you can not depart. Taxi back to gate and go to the hotel. Thats how the US FAR 121 and 135 work.

Most unionized pilot groups negotiate a shorter day, IE max 14 duty day SCHEDULED, but the company can still run you to 16 hours if a delay was mx or wx related.