diff --git a/src/blackmisc/directoryutils.cpp b/src/blackmisc/directoryutils.cpp
index 514fbf2d8..38ae86cdd 100644
--- a/src/blackmisc/directoryutils.cpp
+++ b/src/blackmisc/directoryutils.cpp
@@ -543,19 +543,19 @@ namespace BlackMisc
         return d1.absolutePath() == d2.absolutePath();
     }
 
-    bool CDirectoryUtils::isSubDirectoryOf(const QString &dir1, const QString &dir2)
+    bool CDirectoryUtils::isSameOrSubDirectoryOf(const QString &testDir, const QString &dir2)
     {
-        if (dir1.isEmpty() || dir2.isEmpty()) { return false; }
+        if (testDir.isEmpty() || dir2.isEmpty()) { return false; }
         const QDir d2(dir2);
-        return CDirectoryUtils::isSubDirectoryOf(dir1, d2);
+        return CDirectoryUtils::isSameOrSubDirectoryOf(testDir, d2);
     }
 
-    bool CDirectoryUtils::isSubDirectoryOf(const QString &dir1, const QDir &dir2)
+    bool CDirectoryUtils::isSameOrSubDirectoryOf(const QString &dir1, const QDir &parentDir)
     {
         QDir d1(dir1);
         do
         {
-            if (d1 == dir2) { return true; }
+            if (d1 == parentDir) { return true; }
         }
         while (d1.cdUp());
 
@@ -563,6 +563,14 @@ namespace BlackMisc
         return false;
     }
 
+    bool CDirectoryUtils::isSameOrSubDirectoryOfStringBased(const QString &testDir, const QString &parentDir)
+    {
+        const Qt::CaseSensitivity cs = CFileUtils::osFileNameCaseSensitivity();
+        const QString td = CFileUtils::fixWindowsUncPath(QDir::cleanPath(testDir));
+        const QString pd = CFileUtils::fixWindowsUncPath(QDir::cleanPath(parentDir));
+        return td.contains(pd, cs);
+    }
+
     QSet<QString> CDirectoryUtils::fileNamesToQSet(const QFileInfoList &fileInfoList)
     {
         QSet<QString> sl;
diff --git a/src/blackmisc/directoryutils.h b/src/blackmisc/directoryutils.h
index 4c92edd2a..dee40f256 100644
--- a/src/blackmisc/directoryutils.h
+++ b/src/blackmisc/directoryutils.h
@@ -187,13 +187,17 @@ namespace BlackMisc
         //! Same existing directories
         static bool isSameExistingDirectory(const QString &dir1, const QString &dir2);
 
-        //! Is dir1 a subdirectory (possibly nested) of dir2 or the same directory
+        //! Is "testDir" a subdirectory (possibly nested) of "parentDir" or the same directory
         //! \remark testing on real directory structure
-        static bool isSubDirectoryOf(const QString &dir1, const QString &dir2);
+        static bool isSameOrSubDirectoryOf(const QString &testDir, const QString &parentDir);
 
-        //! Is dir1 a subdirectory (possibly nested) of dir2 or the same directory
+        //! Is "testDir" a subdirectory (possibly nested) of "parentDir" or the same directory
         //! \remark testing on real directory structure
-        static bool isSubDirectoryOf(const QString &dir1, const QDir &dir2);
+        static bool isSameOrSubDirectoryOf(const QString &testDir, const QDir &parentDir);
+
+        //! Is "testDir" a subdirectory (possibly nested) of "parentDir" or the same directory
+        //! \remark String based only
+        static bool isSameOrSubDirectoryOfStringBased(const QString &testDir, const QString &parentDir);
 
         //! Result of directory comparison
         struct DirComparison
diff --git a/src/plugins/simulator/xplane/simulatorxplane.cpp b/src/plugins/simulator/xplane/simulatorxplane.cpp
index c28e9fe3e..41b087f9f 100644
--- a/src/plugins/simulator/xplane/simulatorxplane.cpp
+++ b/src/plugins/simulator/xplane/simulatorxplane.cpp
@@ -576,7 +576,7 @@ namespace BlackSimPlugin
             {
                 Q_ASSERT(package.s.endsWith('/'));
                 package.s.chop(1);
-                if (CDirectoryUtils::isSubDirectoryOf(package.s, simDir))
+                if (CDirectoryUtils::isSameOrSubDirectoryOf(package.s, simDir))
                 {
                     m_trafficProxy->loadPlanesPackage(package.s);
                 }