diff --git a/src/blackmisc/fileutils.cpp b/src/blackmisc/fileutils.cpp
index 7f6bdf725..e9a7ad18c 100644
--- a/src/blackmisc/fileutils.cpp
+++ b/src/blackmisc/fileutils.cpp
@@ -506,6 +506,31 @@ namespace BlackMisc
         return f.left(i);
     }
 
+    QSet<QString> CFileUtils::windowsUncMachines(const QSet<QString> &paths)
+    {
+        if (paths.isEmpty()) { return {}; }
+
+        const Qt::CaseSensitivity cs = osFileNameCaseSensitivity();
+        const bool isCs = isFileNameCaseSensitive();
+
+        QSet<QString> machines;
+        QString lastMachine;
+
+        for (const QString &p : paths)
+        {
+            if (!lastMachine.isEmpty() && p.contains(lastMachine, cs))
+            {
+                // shortcut
+                continue;
+            }
+            const QString m = isCs ? windowsUncMachine(p) : windowsUncMachine(p).toLower();
+            if (m.isEmpty()) { continue; }
+            lastMachine = m;
+            machines.insert(m);
+        }
+        return machines;
+    }
+
     bool CFileUtils::canPingUncMachine(const QString &machine)
     {
         static QMap<QString, qint64> good;
diff --git a/src/blackmisc/fileutils.h b/src/blackmisc/fileutils.h
index e03deff83..a289837c6 100644
--- a/src/blackmisc/fileutils.h
+++ b/src/blackmisc/fileutils.h
@@ -181,6 +181,9 @@ namespace BlackMisc
         //! Machine in Windows UNC path
         static QString windowsUncMachine(const QString &filePath);
 
+        //! All UNC machines from the paths
+        static QSet<QString> windowsUncMachines(const QSet<QString> &paths);
+
         //! Can connect the UNC machine
         static bool canPingUncMachine(const QString &machine);
 
diff --git a/src/blackmisc/simulation/aircraftmodellist.cpp b/src/blackmisc/simulation/aircraftmodellist.cpp
index 4b50ef6d8..8db3fbbc7 100644
--- a/src/blackmisc/simulation/aircraftmodellist.cpp
+++ b/src/blackmisc/simulation/aircraftmodellist.cpp
@@ -8,16 +8,18 @@
 
 #include "blackmisc/simulation/aircraftmodellist.h"
 #include "blackmisc/simulation/matchingutils.h"
+#include "blackmisc/network/networkutils.h"
 #include "blackmisc/aviation/callsign.h"
 #include "blackmisc/aviation/logutils.h"
 #include "blackmisc/math/mathutils.h"
 #include "blackmisc/compare.h"
 #include "blackmisc/iterator.h"
 #include "blackmisc/range.h"
-#include "fileutils.h"
-#include "directoryutils.h"
+#include "blackmisc/fileutils.h"
+#include "blackmisc/directoryutils.h"
 #include "blackmisc/statusmessage.h"
 #include "blackmisc/stringutils.h"
+#include "blackconfig/buildconfig.h"
 
 #include <QStringBuilder>
 #include <QJsonValue>
@@ -27,6 +29,7 @@
 #include <QDir>
 #include <tuple>
 
+using namespace BlackConfig;
 using namespace BlackMisc::Network;
 using namespace BlackMisc::Math;
 using namespace BlackMisc::Aviation;
@@ -1352,6 +1355,22 @@ namespace BlackMisc
             return files;
         }
 
+        QSet<QString> CAircraftModelList::getAllUNCFileNames() const
+        {
+            const bool cs = CFileUtils::isFileNameCaseSensitive();
+            QSet<QString> files;
+            for (const CAircraftModel &model : as_const(*this))
+            {
+                if (!model.hasFileName()) { continue; }
+                const QString fn = (cs ? model.getFileName() : model.getFileNameLowerCase());
+                if (CFileUtils::isWindowsUncPath(fn))
+                {
+                    files.insert(fn);
+                }
+            }
+            return files;
+        }
+
         QString CAircraftModelList::getCombinedTypesAsString(const QString &separator) const
         {
             if (this->isEmpty()) { return {}; }
@@ -1540,6 +1559,13 @@ namespace BlackMisc
             CAircraftModelList sorted(*this);
             if (!alreadySortedByFn) { sorted.sortByFileName(); }
 
+            // avoid hanging if UNC paths are not available
+            if (CBuildConfig::isRunningOnWindowsNtPlatform())
+            {
+                const CStatusMessageList uncMsgs = this->validateUncFiles(sorted.getAllUNCFileNames());
+                if (uncMsgs.hasErrorMessages()) { return uncMsgs; }
+            }
+
             const bool caseSensitive = CFileUtils::isFileNameCaseSensitive();
             const QString simRootDir = CFileUtils::normalizeFilePathToQtStandard(
                                            CFileUtils::stripLeadingSlashOrDriveLetter(
@@ -1615,6 +1641,35 @@ namespace BlackMisc
             return msgs;
         }
 
+        CStatusMessageList CAircraftModelList::validateUncFiles(const QSet<QString> uncFiles) const
+        {
+            // check if UNC paths can be reached
+            CStatusMessageList msgs;
+            if (!CBuildConfig::isRunningOnWindowsNtPlatform()) { return msgs; }
+            if (uncFiles.isEmpty()) { return msgs; }
+
+            const QSet<QString> uncMachines = CFileUtils::windowsUncMachines(uncFiles);
+            if (uncMachines.isEmpty())
+            {
+                msgs.push_back(CStatusMessage(this).validationInfo(u"Found NO UNC machines for %1 files, odd...?") << uncFiles.size());
+            }
+            else
+            {
+                const QString machines = joinStringSet(uncMachines, ", ");
+                msgs.push_back(CStatusMessage(this).validationInfo(u"Found %1 UNC files on machines: %2") << uncFiles.size() << machines);
+            }
+
+            for (const QString &m : uncMachines)
+            {
+                const bool ping = CNetworkUtils::canPing(m);
+                if (!ping)
+                {
+                    msgs.push_back(CStatusMessage(this).validationError(u"Cannot ping UNC machine(s): %1. UNC files: %2") << m << uncFiles.size());
+                }
+            }
+            return msgs;
+        }
+
         QJsonObject CAircraftModelList::toMemoizedJson() const
         {
             CAircraftModel::MemoHelper::CMemoizer helper;
diff --git a/src/blackmisc/simulation/aircraftmodellist.h b/src/blackmisc/simulation/aircraftmodellist.h
index 1a0fa15de..162b9e72c 100644
--- a/src/blackmisc/simulation/aircraftmodellist.h
+++ b/src/blackmisc/simulation/aircraftmodellist.h
@@ -473,6 +473,10 @@ namespace BlackMisc
             //! All file names
             QSet<QString> getAllFileNames() const;
 
+            //! All UNC file names
+            //! \remark Windows on a "shared drive" paths
+            QSet<QString> getAllUNCFileNames() const;
+
             //! All combined types as string
             QString getCombinedTypesAsString(const QString &separator = ", ") const;
 
@@ -555,6 +559,10 @@ namespace BlackMisc
                     const Aviation::CAircraftCategoryList &aircraftCategories = {},
                     const Aviation::CLiveryList &liveries = {},
                     const CDistributorList &distributors = {});
+
+        private:
+            //! Validate UNC paths (Windows)
+            CStatusMessageList validateUncFiles(const QSet<QString> uncFiles) const;
         };
 
         //! Model per callsign