You DOC is an hourly profit, with all your route profit and Misc Profit(Food and Drink Sell) minus your Misc Expense, Staff Expense and Fuel Expense. Then your Monthly Profit is all your total profit in DOC, all your Misc Profit, and all your Leasing Profit(if you are leasing any plane out). Then that total is minused by your one more Daily Fuel Expense, Daily Staff Expense, and Daily Misc Expense(for that day, as it is minused on the month change day too). Then your Monthly profit is minused also by some Monthly Expense(only being payed on Month Change). Those Monthly Expense are Gate Fees(paying the rent on gates), Maintenance Fees(the fee to keep planes running and operating), and finally Lease Expense(the rent you pay for a plane your leasing in your fleet, if you have any). And once you do the math, you'll have your Month Profit.
Hope this Helps
