Per Diem is an hourly rate that is negotiated in the union's CBA. Per diem gets paid differently than straight compensation.The rate of say $1.65 would mean It is computed from the time you are required to be at your duty airport to the time you get released. If you are gone for four days four times in a month, you could get more than $600 tax free. Generally speaking a pilot reports to thier workstation an hour prior to flight time on the first day and ends thier duty 15 minutes after thier last flight. All hours in between are paid at the perdiem rate. This is meant to cover costs while on the road, Food, toiletries, Etc... On average a pilot will earn 3K-4K domestically in perdiem. I would NOT count this towards income becuase you will realize quickly that you really wil spend this cash on food and travel related items once you are at an airline.

Good Luck,
Paul