TheAirline.Models.Airlines.Airline.GetNumberOfEmployees C# (CSharp) Method

        public int GetNumberOfEmployees()
        {
            int instructors = FlightSchools.Sum(f => f.NumberOfInstructors);

            int cockpitCrew = Pilots.Count;
            int cabinCrew =
                Routes.Where(r => r.Type == Route.RouteType.Passenger)
                      .Sum(r => ((PassengerRoute) r).GetTotalCabinCrew());

            int serviceCrew =
                Airports.SelectMany(a => a.GetCurrentAirportFacilities(this))
                        .Where(a => a.EmployeeType == AirportFacility.EmployeeTypes.Support)
                        .Sum(a => a.NumberOfEmployees);
            int maintenanceCrew =
                Airports.SelectMany(a => a.GetCurrentAirportFacilities(this))
                        .Where(a => a.EmployeeType == AirportFacility.EmployeeTypes.Maintenance)
                        .Sum(a => a.NumberOfEmployees);

            return cockpitCrew + cabinCrew + serviceCrew + maintenanceCrew + instructors;
        }