private void FillInPassengersCollection()
 {
     Passengers = PassengersViewModel.GetAllPassengers();
     if (PassengersInFlight != null)
     {
         PassengersInFlight.ForEach(p =>
         {
             if (Passengers.Contains(p.PassengerName))
             {
                 Passengers.Remove(p.PassengerName);
             }
         });
     }
 }