Generally, pay protected for the trip, i.e. if it was worth 45 credits and you are assigned flying for 25, then you will be paid for 45 credits.

I say "generally" because we also have something called OTP (Open Time Priority), which, is a cousin of substitution. You can elect to decline sub, where the sub window is based on the Time Away From Base (and several rules apply), and elect OTP. Now, OTP can be very good or very, very bad. To be honest, that is all anyone needs to know that isn't working here, because the dissertation to finish the overview would take pages and pages.....

Also, I haven't seen any 80 hour trips at FDX, as our normal month is 68 hours (4 week) and 85 for (5 week).