--- a/src/ai/api/ai_airport.cpp	Sun Apr 06 12:26:40 2008 +0000
+++ b/src/ai/api/ai_airport.cpp	Sun Apr 06 14:12:19 2008 +0000
@@ -50,21 +50,15 @@
 
 /* static */ bool AIAirport::BuildAirport(TileIndex tile, AirportType type)
 {
-	if (!::IsValidTile(tile) || type > AT_HELISTATION) {
-		AIObject::SetLastError(AIError::ERR_PRECONDITION_FAILED);
-		return false;
-	}
-
+	EnforcePrecondition(false, ::IsValidTile(tile));
+	EnforcePrecondition(false, type <= AT_HELISTATION);
 	return AIObject::DoCommand(tile, type, 0, CMD_BUILD_AIRPORT);
 }
 
 /* static */ bool AIAirport::RemoveAirport(TileIndex tile)
 {
-	if (!::IsValidTile(tile) || !(IsAirportTile(tile) || IsHangarTile(tile))) {
-		AIObject::SetLastError(AIError::ERR_PRECONDITION_FAILED);
-		return false;
-	}
-
+	EnforcePrecondition(false, ::IsValidTile(tile))
+	EnforcePrecondition(false, IsAirportTile(tile) || IsHangarTile(tile));
 	return AIObject::DoCommand(tile, 0, 0, CMD_LANDSCAPE_CLEAR);
 }