public async Task <List <Person> > GetFlightPassengers(string flightNumber)
        {
            if (String.IsNullOrEmpty(flightNumber))
            {
                throw new Exception("Flight Number is required");
            }

            var flightRep  = new FlightRepository();
            var bookingRep = new BookingRepository();

            var f = flightRep.GetFlightByNumber(flightNumber);

            if (f == null)
            {
                throw new Exception("Flight not found");
            }

            var booking    = bookingRep.GetBookingByFlightId(f.Id);
            var passengers = booking.Passengers;

            return(passengers.ToList());
        }