private void SearchDestinationAirportIDButton_Click(object sender, EventArgs e)
        {
            SelectAirportPage a = new SelectAirportPage(reservationSystem);

            a.SetIIDSelectionCallBack(new IDSelectionCallBack(SetDestinationAirportID));
            a.ShowDialog();
        }
 private void SearchOriginAirportIDButton_Click(object sender, EventArgs e)
 {
     SelectAirportPage a = new SelectAirportPage(reservationSystem);
     a.SetIIDSelectionCallBack(new IDSelectionCallBack(SetOriginAirportID));
     a.ShowDialog();
 }