diff --git a/src/airport.h b/src/airport.h
--- a/src/airport.h
+++ b/src/airport.h
@@ -37,7 +37,8 @@ enum {
 	AT_INTERCON      =   7,
 	AT_HELISTATION   =   8,
 	AT_OILRIG        =   9,
-	NUM_AIRPORTS     =  10,
+	NEW_AIRPORT_OFFSET = 10,
+	NUM_AIRPORTS     =  128,
 	AT_DUMMY         = 255
 };
 
diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -63,7 +63,7 @@ void AirportSpec::ResetAirports()
 {
 	extern const AirportSpec _origin_airport_specs[];
 	memset(&AirportSpec::specs, 0, sizeof(AirportSpec::specs));
-	memcpy(&AirportSpec::specs, &_origin_airport_specs, sizeof(AirportSpec) * NUM_AIRPORTS);
+	memcpy(&AirportSpec::specs, &_origin_airport_specs, sizeof(AirportSpec) * NEW_AIRPORT_OFFSET);
 }
 
 /**
diff --git a/src/table/airport_defaults.h b/src/table/airport_defaults.h
--- a/src/table/airport_defaults.h
+++ b/src/table/airport_defaults.h
@@ -404,7 +404,7 @@ extern const AirportSpec _origin_airport
 	AS_GENERIC(&_airportfta_oilrig, NULL, 0, NULL, 0, 1, 1, 0, 4, 0, 0, ATP_TTDP_OILRIG, APC_HELIPORT, STR_NULL, false),
 };
 
-assert_compile(NUM_AIRPORTS == lengthof(_origin_airport_specs));
+assert_compile(NEW_AIRPORT_OFFSET == lengthof(_origin_airport_specs));
 
 #undef AS
 #undef AS_ND