diff --git a/AirlineServer/AirlineServer/Models/Airport.cs b/AirlineServer/AirlineServer/Models/Airport.cs
index 878c2a6..5e75fab 100644
--- a/AirlineServer/AirlineServer/Models/Airport.cs
+++ b/AirlineServer/AirlineServer/Models/Airport.cs
@@ -10,6 +10,6 @@ namespace AirlineServer.Models
         [DataMember]
         public string Name { get; set; }
         [DataMember]
-        public City City { get; set; }
+        public virtual City City { get; set; }
     }
 }
diff --git a/AirlineServer/AirlineServer/Models/Flight.cs b/AirlineServer/AirlineServer/Models/Flight.cs
index 12d42ac..ecac3a1 100644
--- a/AirlineServer/AirlineServer/Models/Flight.cs
+++ b/AirlineServer/AirlineServer/Models/Flight.cs
@@ -9,7 +9,7 @@ namespace AirlineServer.Models
         [DataMember]
         public int FlightID { get; set; }
         [DataMember]
-        public Airline Airline { get; set; }
+        public virtual Airline Airline { get; set; }
         [DataMember]
         public string Name { get; set; }
         [DataMember]
@@ -17,9 +17,9 @@ namespace AirlineServer.Models
         [DataMember]
         public float Duration { get; set; }
         [DataMember]
-        public Airport Origin { get; set; }
+        public virtual Airport Origin { get; set; }
         [DataMember]
-        public Airport Destination { get; set; }
+        public virtual Airport Destination { get; set; }
         public int MaxSeats { get; set; }
         public int BookedSeats { get; set; }
     }
diff --git a/Plattform/Plattform/Models/Flight.cs b/Plattform/Plattform/Models/Flight.cs
index ec7876d..75db37f 100644
--- a/Plattform/Plattform/Models/Flight.cs
+++ b/Plattform/Plattform/Models/Flight.cs
@@ -9,7 +9,7 @@ namespace Plattform.Models
         [DataMember]
         public int FlightID { get; set; }
         [DataMember]
-        public Airline Airline { get; set; }
+        public virtual Airline Airline { get; set; }
         [DataMember]
         public string Name { get; set; }
         [DataMember]
@@ -17,9 +17,9 @@ namespace Plattform.Models
         [DataMember]
         public float Duration { get; set; }
         [DataMember]
-        public string FromCityShortName { get; set; }
+        public virtual Airport Origin { get; set; }
         [DataMember]
-        public string ToCityShortName { get; set; }
+        public virtual Airport Destination { get; set; }
 
         public Flight (AirlineService.Flight flight)
         {
diff --git a/Plattform/Plattform/Models/Hotel.cs b/Plattform/Plattform/Models/Hotel.cs
index 8fa77a2..ead9087 100644
--- a/Plattform/Plattform/Models/Hotel.cs
+++ b/Plattform/Plattform/Models/Hotel.cs
@@ -10,6 +10,6 @@ namespace Plattform.Models
         [DataMember]
         public int Name { get; set; }
         [DataMember]
-        public City City { get; set; }
+        public virtual City City { get; set; }
     }
 }