diff --git a/aman/sys/aco/Node.py b/aman/sys/aco/Node.py
index ed2af92..5aba418 100644
--- a/aman/sys/aco/Node.py
+++ b/aman/sys/aco/Node.py
@@ -155,7 +155,7 @@ class Node:
         self.PredictedDistanceToIAF = inbound.Report.distanceToIAF
         self.PredictedCoordinate = [ inbound.CurrentPosition.latitude, inbound.CurrentPosition.longitude ]
         self.PredictionTime = referenceTime
-        self.ArrivalCandidates = {}
+        self.ArrivalCandidates = None
         self.Inbound = inbound
 
         if None == referenceTime or None == sequencingConfig:
@@ -185,6 +185,7 @@ class Node:
                 self.PredictedCoordinate = prediction
 
         setEnrouteTime = None == self.Inbound.EnrouteArrivalTime
+        self.ArrivalCandidates = {}
 
         # calculate the timings for the different arrival runways
         for identifier in sequencingConfig.ActiveArrivalRunways: