diff --git a/aviation_planning/airlineplanning.ipynb b/aviation_planning/airlineplanning.ipynb
index 18c8f75..781b2dd 100644
--- a/aviation_planning/airlineplanning.ipynb
+++ b/aviation_planning/airlineplanning.ipynb
@@ -667,8 +667,8 @@
     "deltaminus_flightarcs = {}\n",
     "for a in aircraft_flights:\n",
     "    aircraft_flights[a] += ['source_%s'%a,'sink_%s'%a]\n",
-    "    flight_origin['source_%s'%a] = aircrafts_startpositions_airc[a]\n",
-    "    flight_dest['source_%s'%a] = aircrafts_endpositions_airc[a]\n",
+    "    flight_origin['source_%s'%a] = aircrafts_endpositions_airc[a]\n",
+    "    flight_dest['source_%s'%a] = aircrafts_startpositions_airc[a]\n",
     "    flight_origin['sink_%s'%a] = aircrafts_endpositions_airc[a]\n",
     "    flight_dest['sink_%s'%a] = aircrafts_startpositions_airc[a]\n",
     "\n",
@@ -687,7 +687,12 @@
     "            if f1!=f2 and flight_end_time[f1] < flight_start_time[f2] and flight_dest[f1] == flight_origin[f2]: \n",
     "                flight_arcs_for_each_aircraft[a].append((f1,f2))\n",
     "                deltaplus_flightarcs[a][f1].append(f2)\n",
-    "                deltaminus_flightarcs[a][f2].append(f1) \n"
+    "                deltaminus_flightarcs[a][f2].append(f1) \n",
+    "            # allow to connect source and target directly for the case that aircraft is not used at all    \n",
+    "            elif str(f1).startswith('source') and str(f2).startswith('sink'):\n",
+    "                flight_arcs_for_each_aircraft[a].append((f1,f2))\n",
+    "                deltaplus_flightarcs[a][f1].append(f2)\n",
+    "                deltaminus_flightarcs[a][f2].append(f1)"
    ]
   },
   {