diff --git a/src/airport.cpp b/src/airport.cpp
--- a/src/airport.cpp
+++ b/src/airport.cpp
@@ -488,14 +488,14 @@ uint32 GetValidAirports()
 {
 	uint32 mask = 0;
 
-	if (_cur_year <  1960 || _patches.always_small_airport) SETBIT(mask, 0);  // small airport
-	if (_cur_year >= 1955) SETBIT(mask, 1); // city airport
-	if (_cur_year >= 1963) SETBIT(mask, 2); // heliport
-	if (_cur_year >= 1980) SETBIT(mask, 3); // metropolitan airport
-	if (_cur_year >= 1990) SETBIT(mask, 4); // international airport
-	if (_cur_year >= 1983) SETBIT(mask, 5); // commuter airport
-	if (_cur_year >= 1976) SETBIT(mask, 6); // helidepot
-	if (_cur_year >= 2002) SETBIT(mask, 7); // intercontinental airport
-	if (_cur_year >= 1980) SETBIT(mask, 8); // helistation
+	if (_cur_year <  1960 || _patches.always_small_airport) SetBit(mask, 0);  // small airport
+	if (_cur_year >= 1955) SetBit(mask, 1); // city airport
+	if (_cur_year >= 1963) SetBit(mask, 2); // heliport
+	if (_cur_year >= 1980) SetBit(mask, 3); // metropolitan airport
+	if (_cur_year >= 1990) SetBit(mask, 4); // international airport
+	if (_cur_year >= 1983) SetBit(mask, 5); // commuter airport
+	if (_cur_year >= 1976) SetBit(mask, 6); // helidepot
+	if (_cur_year >= 2002) SetBit(mask, 7); // intercontinental airport
+	if (_cur_year >= 1980) SetBit(mask, 8); // helistation
 	return mask;
 }