If you show up for a trip you are pay protected for that trip. If they do not use you then you get 75 hrs of pay for the month but if you fly more then 75 then you get paid the additional flight time on the middle of the month paycheck. You get per diem only when you are on a trip and it adds up to around 225-300 a month tax free if it is for multi-day trips. It is all in the contract and will be fairly straightforward.