Fix for deleting flights when importing (#984)

app/Services/ImportService.php

@@ -6,6 +6,8 @@ use App\Contracts\ImportExport;
 use App\Contracts\Service;
 use App\Models\Airport;
 use App\Models\Expense;
+use App\Models\Flight;
+use App\Models\FlightFieldValue;
 use App\Repositories\FlightRepository;
 use App\Services\ImportExport\AircraftImporter;
 use App\Services\ImportExport\AirportImporter;
@@ -229,7 +231,8 @@ class ImportService extends Service
     public function importFlights($csv_file, bool $delete_previous = true)
     {
         if ($delete_previous) {
-            // TODO: Delete all from: flights, flight_field_values
+            Flight::truncate();
+            FlightFieldValue::truncate();
         }
 
         $importer = new FlightImporter();