diff --git a/aman/sys/aco/RunwayManager.py b/aman/sys/aco/RunwayManager.py
index fb6ee22..efa120f 100644
--- a/aman/sys/aco/RunwayManager.py
+++ b/aman/sys/aco/RunwayManager.py
@@ -20,37 +20,26 @@ class RunwayManager:
             if not runway.Runway.Name in self.RunwayInbounds:
                 self.RunwayInbounds[runway.Runway.Name] = None
 
-    def validateWtc(inbound : Inbound):
-        wtc = inbound.Report.aircraft.wtc.upper()
-        if 'L' == wtc or 'M' == wtc or 'H' == wtc or 'J' == wtc:
-            return wtc
-        else:
-            return None
-
     def calculateEarliestArrivalTime(self, runway : str, inbound : Inbound, useITA : bool, earliestArrivalTime : datetime):
-        earliestArrivalTimes = []
+        constrainedETA = None
 
         if None != self.RunwayInbounds[runway]:
             # get the WTC based ETA
-            wtcPre = RunwayManager.validateWtc(self.RunwayInbounds[runway])
-            wtcThis = RunwayManager.validateWtc(inbound)
-            if None == wtcPre or None == wtcThis:
-                spacing = 3
+            if None == self.RunwayInbounds[runway].WTC or None == inbound.WTC:
+                spacingWTC = 3
             else:
-                spacing = self.Spacings[wtcPre][wtcThis]
-            delay = timedelta(minutes = spacing / (inbound.PerformanceData.SpeedApproach / 60))
-            earliestArrivalTimes.append(self.RunwayInbounds[runway].PlannedArrivalTime + delay)
+                spacingWTC = self.Spacings[self.RunwayInbounds[runway].WTC][inbound.WTC]
 
             # get the runway time spacing
-            spacing = self.Configuration.RunwayConstraints.findRunway(runway).Spacing
-            delay = timedelta(minutes = spacing / (inbound.PerformanceData.SpeedApproach / 60))
-            earliestArrivalTimes.append(self.RunwayInbounds[runway].PlannedArrivalTime + delay)
+            spacingRunway = self.Configuration.RunwayConstraints.findRunway(runway).Spacing
+            constrainedETA = self.RunwayInbounds[runway].PlannedArrivalTime + timedelta(minutes = max(spacingWTC, spacingRunway) / (inbound.PerformanceData.SpeedApproach / 60))
 
         # calculate the arrival times for the dependent inbounds
         for dependentRunway in self.Configuration.RunwayConstraints.findDependentRunways(runway):
             if None != self.RunwayInbounds[dependentRunway.Runway.Name]:
-                delay = timedelta(minutes = 3 / (inbound.PerformanceData.SpeedApproach / 60))
-                earliestArrivalTimes.append(self.RunwayInbounds[dependentRunway.Runway.Name].PlannedArrivalTime + delay)
+                candidate = self.RunwayInbounds[dependentRunway.Runway.Name].PlannedArrivalTime + timedelta(minutes = 3 / (inbound.PerformanceData.SpeedApproach / 60))
+                if None == constrainedETA or candidate > constrainedETA:
+                    constrainedETA = candidate
 
         # get the arrival time on the runway of the inbound
         if True == useITA:
@@ -58,19 +47,17 @@ class RunwayManager:
         else:
             arrivalTime = inbound.ArrivalCandidates[runway].InitialArrivalTime
 
-        if 0 == len(earliestArrivalTimes):
-            return arrivalTime, timedelta(seconds = 0)
+        if None == constrainedETA:
+            return max(arrivalTime, earliestArrivalTime), timedelta(seconds = 0)
         else:
-            eta = max(earliestArrivalTimes)
+            eta = max(constrainedETA, earliestArrivalTime)
             if eta < arrivalTime:
                 return arrivalTime, arrivalTime - eta
             else:
                 return eta, timedelta(seconds = 0)
 
     def selectArrivalRunway(self, inbound : Inbound, useITA : bool, earliestArrivalTime : datetime):
-        availableRunways = []
-        for runway in self.Configuration.RunwayConstraints.ActiveArrivalRunways:
-            availableRunways.append(runway)
+        availableRunways = self.Configuration.RunwayConstraints.ActiveArrivalRunways
 
         #if 1 < len(availableRunways):
             # TODO filter based on type