diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -39,9 +39,9 @@ struct AirportScopeResolver : public Sco
 	{
 	}
 
-	/* virtual */ uint32 GetRandomBits() const;
-	/* virtual */ uint32 GetVariable(byte variable, uint32 parameter, bool *available) const;
-	/* virtual */ void StorePSA(uint pos, int32 value);
+	uint32 GetRandomBits() const override;
+	uint32 GetVariable(byte variable, uint32 parameter, bool *available) const override;
+	void StorePSA(uint pos, int32 value) override;
 };
 
 /** Resolver object for airports. */
@@ -51,7 +51,7 @@ struct AirportResolverObject : public Re
 	AirportResolverObject(TileIndex tile, Station *st, byte airport_id, byte layout,
 			CallbackID callback = CBID_NO_CALLBACK, uint32 callback_param1 = 0, uint32 callback_param2 = 0);
 
-	/* virtual */ ScopeResolver *GetScope(VarSpriteGroupScope scope = VSG_SCOPE_SELF, byte relative = 0)
+	ScopeResolver *GetScope(VarSpriteGroupScope scope = VSG_SCOPE_SELF, byte relative = 0) override
 	{
 		switch (scope) {
 			case VSG_SCOPE_SELF: return &this->airport_scope;
@@ -59,7 +59,7 @@ struct AirportResolverObject : public Re
 		}
 	}
 
-	/* virtual */ const SpriteGroup *ResolveReal(const RealSpriteGroup *group) const;
+	const SpriteGroup *ResolveReal(const RealSpriteGroup *group) const override;
 };
 
 /**