B2N2
You get charged per day or portion of a day that you have the car in your posession, why would it need to be different for an aircraft?
Quite true you get charged a price for the day and in most unlimited mileage rentals they dont care whether you do 1 mile or 600 miles in that day.
Wish the same was true with aircraft
I would love to go touring for the day around france with just fuel to pay and as many miles as I could cram in
Pace