diff --git a/src/newgrf_airport.h b/src/newgrf_airport.h
--- a/src/newgrf_airport.h
+++ b/src/newgrf_airport.h
@@ -51,6 +51,7 @@ enum TTDPAirportType {
 struct AirportSpec {
 	const struct AirportFTAClass *fsm;     ///< the finite statemachine for the default airports
 	const AirportTileTable * const *table; ///< list of the tiles composing the airport
+	byte num_table;                        ///< number of elements in the table
 	const TileIndexDiffC *depot_table;     ///< gives the position of the depots on the airports
 	byte nof_depots;                       ///< the number of depots in this airport
 	byte size_x;                           ///< size of airport in x direction