public static object ShowPopUp(AirlinerType airliner, List <AirlinerClass> classes)
        {
            PopUpWindow window = new PopUpAirlinerConfiguration(airliner, classes);

            window.ShowDialog();

            return(window.Selected);
        }
        public static object ShowPopUp(Airliner airliner)
        {
            PopUpWindow window = new PopUpAirlinerConfiguration(airliner);

            window.ShowDialog();

            return(window.Selected);
        }
        public static object ShowPopUp(AirlinerType airliner, List<AirlinerClass> classes)
        {
            PopUpWindow window = new PopUpAirlinerConfiguration(airliner,classes);
            window.ShowDialog();

            return window.Selected;
        }
        public static object ShowPopUp(Airliner airliner)
        {
            PopUpWindow window = new PopUpAirlinerConfiguration(airliner);
            window.ShowDialog();

            return window.Selected;
        }