Update v11

[Kaiii3]

and one more:

This time when trying to open the Airport (OSL) from inside the demand-view from an Airport:

15.03.2018: 15:25 System.NullReferenceException: Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt.
bei TheAirlineProjectV2.Modules.Airport.ViewModels.AirportViewModel.setProperties() in C:\Users\Christian\Documents\Visual Studio 2017\Projects\TheAirlineProjectV2\TheAirlineProjectV2.Modules.Airport\ViewModels\AirportViewModel.cs:Zeile 143.
bei TheAirlineProjectV2.Modules.Airport.ViewModels.AirportViewModel.set_CurrentAirport(Airport value) in C:\Users\Christian\Documents\Visual Studio 2017\Projects\TheAirlineProjectV2\TheAirlineProjectV2.Modules.Airport\ViewModels\AirportViewModel.cs:Zeile 126.
bei TheAirlineProjectV2.Modules.Airport.Controllers.AirportController.AirportChanged(String id) in C:\Users\Christian\Documents\Visual Studio 2017\Projects\TheAirlineProjectV2\TheAirlineProjectV2.Modules.Airport\Controllers\AirportController.cs:Zeile 62.
bei Prism.Events.EventSubscription`1.<>c__DisplayClass11_0.<GetExecutionStrategy>b__0(Object[] arguments)
bei Prism.Events.EventBase.InternalPublish(Object[] arguments)
bei TheAirlineProjectV2.GraphicsControls.Commands.AirportCommand.OnExecute(Object parameter) in C:\Users\Christian\Documents\Visual Studio 2017\Projects\TheAirlineProjectV2\TheAirlineProjectV2.GraphicsControls\Commands\AirportCommand.cs:Zeile 26.
bei FirstFloor.ModernUI.Presentation.CommandBase.Execute(Object parameter)
bei MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
bei System.Windows.Documents.Hyperlink.OnClick()
bei System.Windows.Documents.Hyperlink.DoUserInitiatedNavigation(Object sender)
bei System.Windows.Documents.Hyperlink.OnMouseLeftButtonUp(Object sender, MouseButtonEventArgs e)
bei System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
bei System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
bei System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
bei System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
bei System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
bei System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
bei System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
bei System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
bei System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
bei System.Windows.ContentElement.RaiseTrustedEvent(RoutedEventArgs args)
bei System.Windows.Input.InputManager.ProcessStagingArea()
bei System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
bei System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
bei System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
bei System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
bei System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
bei MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
bei MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
bei System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
bei System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
bei System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
bei MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
bei MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
bei System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
bei System.Windows.Application.RunDispatcher(Object ignore)
bei System.Windows.Application.RunInternal(Window window)
bei TheAirlineProjectV2.App.Main()

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and one more, this time no CTD, but an simple bug.

I bought an Lookheed 749 in 1950, which can handle up to 2 classes. The airliner is deliverd with just one class (first) when I'm trying to add a new class (eco) I get the error, the the maximum number of classes is already reached