Circle Case study

Boosting Heathrow’s Departure Efficiency

An award-winning new approach to aircraft stand and take-off slot allocations has enabled Heathrow to become more efficient.


  • Minimise aircraft turnaround delays – often the main cause of airfield congestion
  • Optimise aircraft stand and taxiway provisioning
  • Move away from manual aircraft-to-tower communications as the primary method of aircraft routing on the ground


  • Working with the University of Nottingham – who developed new algorithms – CACI’s Digital Solutions team developed the Target Start-up Approval Time (TSAT) pre-departure sequencing system
  • The solution uses a tailored algorithm to analyse multiple variables and suggest optimal aircraft movement times
  • Aircraft stands are now allocated well ahead of time and take-off slots are decided based on several factors including wake turbulence and aircrew checklist completion
  • Using TSAT, aircraft are now held at their stands for longer based on slot allocation and engine start is delayed – significantly reducing fuel burn and, therefore, the cost to airlines.


  • 100% of aircraft stands allocated 20 minutes before arrival
  • Improved customer satisfaction and airport performance
  • Decreased fuel burn is saving airlines millions in costs
  • Project was a key factor in our partners 2019 Real IT Award win for Turning Data into Insights

“The Airport Collaborative Decision Making system ensures that the correct number &  type of aircraft leave the gate and arrive at the runway at the right time. This increased throughput and reduced congestion. With the complexity of the operation at Heathrow, we needed to use the most advanced systems to deliver the benefits we were seeking and CACI provided just that.”

John Crook, Business Support Manager, NATS Heathrow


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