Jared_Maurtua wrote on May 20^th, 2012 at 3:02am:

What is PTD and what does it do? :-?

It allows you to leave your flightin progress (like if you need to go to bed), and when you come back, the Flight Simulator is paused (often 10-20nm before the TOD) and allowing you to prepare and continue the rest of your flight. Captain Sim don't have this feature on any of their aircraft for FSX (I don't know about their FS9 aircraft as I never bought any), but many have asked for it.

Hope that helps explain it.

Mark