public string Get(string relative_to)
 {
     string requestString = Request.QueryString.Value;
     bool isExternals = requestString.Contains("sync_all");
     List<Flight> flights = serverM.GetFlights(relative_to, isExternals);
     string response = "";
     foreach (Flight flight in flights)
     {
         response += JsonConvert.SerializeObject(flight);
     }
     return response;
 }