he airline AirForm proposes us to model in UML a reduced version of its information system of reservation of flight tickets. Flights are planned in advance and assigned to an airplane, an airport of departure, an airport of arrival, a departure date and an arrival date. Each airplane has a capacity in maximum number of passengers. Tickets are issued for each flight when planning, there is no overbooking.

Users buy the tickets. This purchase results in a reservation (via ticket) for the flight in question. We keep the last names, first names, addresses and phones of the users who made a reservation, as well as the booking date and the ticket price. Upon check-in (departure), passengers confirm their tickets for the registered flight. We memorize this initial confirmation.

When the flight is over, the reservations associated with it are archived, and they are deleted when the flight is canceled.

1. Write the high-level use case Buy the tickets initiated by a customer, and refine if it is possible this high-level use case.