10:30am Curriculum presentation
12pm Student interview
Then, the faculty interview can be anywhere from 1pm on. Mine was at 3, so I had a couple hours idle time. If you need to know the exact time of your appt, call.
My interview supposed to be at 3:30 which was one of the later interviews. But the guy was late which was cool cuz the guy was so laid back there was no reason to stress. Anyway most of the people on my interview day were done and gone by 4 or so. Hope that helps. Most of them stayed an extra night b/c like you said there are not that many late flights out of the Pitt.
Keep in mind that the airport is anywhere from 30 minutes to an hour away depending on traffic and whether or not the Fort Pitt Bridge is open or closed. So it might be cutting it close if you're trying to get out before six.