static void Main(string[] args)
        {
            String          choice;
            CustomerService _customerService = new CustomerService();
            FlightService   _flightService   = new FlightService();

            do
            {
                Console.WriteLine("------------------------MENU---------------------");
                Console.WriteLine("1. Create flights \n" +
                                  "2. Create customers \n" +
                                  "3. Add customers to flight \n" +
                                  "4. Book flight for customer \n" +
                                  "5. Search flight \n" +
                                  "6. Search customer \n" +
                                  "7. Get all flight informations \n" +
                                  "8. Get all customer information \n" +
                                  "9. Exit ");
                choice = Console.ReadLine();
                choice.Trim();
                switch (choice)
                {
                case Constants.CREATE_FLIGHT:
                    _flightService.GetFlightInfo(listOfFlight);
                    break;

                case Constants.CREATE_CUSTOMER:
                    _customerService.GetCustomerInfo(listOfCustomer);
                    break;

                case Constants.ADD_CUSTOMER:
                    _flightService.AddCustomer(listOfFlight);
                    break;

                case Constants.ADD_FLIGHT:
                    _customerService.AddFlight(listOfCustomer);
                    break;

                case Constants.SEARCH_FLIGHT:
                    _flightService.SearchFlight(listOfFlight);
                    break;

                case Constants.SEARCH_CUSTOMER:
                    _customerService.SearchCustomer(listOfCustomer);
                    break;

                case Constants.GET_ALL_FLIGHT:
                    _flightService.PrintFlight(listOfFlight);
                    break;

                case Constants.GET_ALL_CUSTOMER:
                    _customerService.PrintCustomers(listOfCustomer);
                    break;

                default:
                    choice = Constants.EXIT;
                    break;
                }
            } while (!choice.Equals(Constants.EXIT));
        }