do not delete the airports

src/PlugIn.cpp

@@ -683,7 +683,8 @@ void PlugIn::OnTimer(int counter) {
     if (EuroScopePlugIn::CONNECTION_TYPE_NO == this->GetConnectionType()) {
         if (true == this->m_connectedToNetwork) {
             std::lock_guard guardUpdate(this->m_updateQueueLock);
-            this->m_updateQueue.clear();
+            for (auto& airport : this->m_updateQueue)
+                airport.second.clear();
 
             std::lock_guard guardInbound(this->m_inboundsQueueLock);
             this->m_inbounds.clear();