public async Task <IEnumerable <Flight> > Get([FromQuery] DateTime relative_to)
        {
            bool          isExternal = Request.QueryString.Value.Contains("sync_all");
            List <Flight> flights    = new List <Flight>();
            List <string> flightsIDs = (List <string>)_flightPlansDataBase.GetAllKeys();

            foreach (string id in flightsIDs)
            {
                FlightPlan plan = _flightPlansDataBase.GetById(id);
                if (plan.InFlightRelativeTo(relative_to))
                {
                    var    tuple  = plan.Interpolate(relative_to);
                    Flight flight = new Flight(id, tuple.Item1, tuple.Item2,
                                               plan.Passengers, plan.CompanyName, relative_to, false);
                    flights.Add(flight);
                }
            }
            if (isExternal)
            {
                flights.AddRange(await GetExternalFlights(relative_to));
            }
            return(flights);
        }