There are two sides to this. If you expense everything, you can always eat decent and don't have to pinch in certain locales (Aspen where everything is expensive). On the other hand, if you are per diem, sometimes you come away with money in your pocket. I guess it depends on how good the per diem rate is and if the company is willing to provide "special" per diem for trips to expensive locations (ours doesn't).
that aside, let me answer your question:
normal: $1.80/hour = 43.20 for the day (24 hrs) anything domestic
special: $2.80/hour = 67.20 for the day (24 hrs) anything international, or trips that fall on a weekend or holiday, we also get this when we go to school.
Both rates start from the time you go wheels up at home base until wheels down at home base
Like I said above, I've come out waaaay ahead on certain trips (school-you don't have time to spend alot of money!) but I've also come out behind at places like Aspen...and that's just eating normal meals, no steaks, no brews! I think in the long run, expense accounts save the company money. I know I've done alot of fun stuff on my per diem that wasn't "meal-related" (i.e. sea-kayaking, skiing, etc.).
edited for: We are 98% part 91, 2% part 135
(I second the $100/day mentioned below!)