diff --git a/src/newgrf_airport.h b/src/newgrf_airport.h
--- a/src/newgrf_airport.h
+++ b/src/newgrf_airport.h
@@ -72,7 +72,7 @@ struct AirportSpec {
 	Year max_year;                         ///< last year the airport is available
 	StringID name;                         ///< name of this airport
 	TTDPAirportType ttd_airport_type;      ///< ttdpatch airport type (Small/Large/Helipad/Oilrig)
-	AirportClassID aclass;                 ///< the class to which this airport type belongs
+	AirportClassID cls_id;                 ///< the class to which this airport type belongs
 	SpriteID preview_sprite;               ///< preview sprite for this airport
 	/* Newgrf data */
 	bool enabled;                          ///< entity still avaible (by default true).newgrf can disable it, though