diff --git a/src/blackmisc/aviation/flightplan.cpp b/src/blackmisc/aviation/flightplan.cpp
index 240511ff5..309e520fd 100644
--- a/src/blackmisc/aviation/flightplan.cpp
+++ b/src/blackmisc/aviation/flightplan.cpp
@@ -463,17 +463,24 @@ namespace BlackMisc
             return CFlightPlan();
         }
 
-        const QString CFlightPlan::flightRuleToString(CFlightPlan::FlightRules rule)
+        const QString &CFlightPlan::flightRuleToString(CFlightPlan::FlightRules rule)
         {
+            static const QString v("VFR");
+            static const QString i("IFR");
+            static const QString s("SVFR");
+            static const QString d("DVFR");
+            static const QString unknown("???");
+
             switch (rule)
             {
-            case VFR:  return QLatin1String("VFR");
-            case IFR:  return QLatin1String("IFR");
-            case SVFR: return QLatin1String("SVFR");
-            case DVFR: return QLatin1String("DVFR");
+            case VFR:  return v;
+            case IFR:  return i;
+            case SVFR: return s;
+            case DVFR: return d;
             case UNKNOWN:
-            default:   return QLatin1String("???");
+            default: break;
             }
+            return unknown;
         }
 
         QString CFlightPlan::aircraftIcaoCodeFromEquipmentCode(const QString &equipmentCodeAndAircraft)
diff --git a/src/blackmisc/aviation/flightplan.h b/src/blackmisc/aviation/flightplan.h
index 7771084c8..3fa8f933a 100644
--- a/src/blackmisc/aviation/flightplan.h
+++ b/src/blackmisc/aviation/flightplan.h
@@ -378,7 +378,7 @@ namespace BlackMisc
             static CFlightPlan loadFromMultipleFormats(const QString &fileName, CStatusMessageList *msgs = nullptr);
 
             //! Rules to string
-            static const QString flightRuleToString(FlightRules rule);
+            static const QString &flightRuleToString(FlightRules rule);
 
             //! String to flight rules
             static FlightRules stringToFlightRules(const QString &flightRules);