diff --git a/src/aircraft_gui.cpp b/src/aircraft_gui.cpp
--- a/src/aircraft_gui.cpp
+++ b/src/aircraft_gui.cpp
@@ -36,7 +36,7 @@ void DrawAircraftDetails(const Aircraft 
 	int y_offset = (v->Next()->cargo_cap != 0) ? -(FONT_HEIGHT_NORMAL + 1): 0;
 	Money feeder_share = 0;
 
-	for (const Aircraft *u = v; u != NULL; u = u->Next()) {
+	for (const Aircraft *u = v; u != nullptr; u = u->Next()) {
 		if (u->IsNormalAircraft()) {
 			SetDParam(0, u->engine_type);
 			SetDParam(1, u->build_year);