Scotia Airlines is a new budget airline operating between Glasgow Airport and the Western Isles. It operates two 24-seater light passenger aircraft and requires a flight booking system. Because Scotia offers low cost air travel, there is a need to treat each flight as single cost centre and to be able to ascertain, at any moment, the amount of the cash taken for that flight. Reservations and bookings cannot be made until the flight details have been finalised (flight number, departure and arrival airports). A seat on a flight is considered booked when payment as been received for it. When a reservation is confirmed (changed to booked), the passenger name is checked against the original reservation. A flight can be in any of the following states: Available for bookings Checking in Boarding Closed