Automation - Aircraft Flow Management

Flow management is an Air Traffic Management (ATM) tool used by controllers and airlines to better manage the flow of aircraft into airports. Airports have limited capacity due to factors such as the number of runways, airspace restrictions and the level of traffic that air traffic control can safely handle. Automation of the traffic flow process enables more efficient aircraft sequencing resulting in better runway utilisation, less airborne holding and greater fuel efficiency. As Air Navigation Service Providers (ANSPs) and airlines seek new ways to reduce costs and improve safety, arrival and flow management tools are becoming increasingly popular with a number of industry players operating in this highly competitive market.

Human Factors play an important role in flow management. Automation and standardisation of procedures increases safety and reduces the chance of error. Sequencing can occur at a critical stage of flight and by removing the requirement to hold or vector the aircraft; pilots have more time to prepare the aircraft for landing.

How Flow Management works

Most airports and air traffic control sectors have a published maximum capacity. Once this level is reached, steps are taken to reduce traffic. This generally results in airborne holding or additional turns (vectoring) to delay traffic and create space. Delays are inefficient and costly to airlines. It is more efficient to delay the departure of an aircraft - therefore holding it on the ground with the engines off.

Under the flow management system, aircraft are allocated a slot time which aligns with the Expected Time of Arrival (ETA) at the destination. The slot time is also referred to as a CTOT (Calculated Take-Off Time). The CTOT is passed to the aircraft with the initial clearance and advises the pilot of the time required to be at the runway ready for departure. Provided the slot time/CTOT is adhered to, the aircraft should expect an uninterrupted efficient flight.

The automated system is highly complex and can take into account weather delays and inflight rerouting to re-sequence flights. In Europe, flow management systems can synchronise information from many different airports to manage departures and avoid congestion along routes. An arrival manager will determine the arrival sequence and advise controllers of time requirements to be passed to pilots in order to achieve the desired sequence.

In New Zealand, Airways operate the flow management system CAM (Collaborative Arrivals Manager). This online tool enables the airlines and Airways to work together to avoid congestion and unnecessary delays through better scheduling of arrivals and departures at Auckland, Wellington and Christchurch airports.

Slot bookings for aircraft flying into Auckland Airport (image embedded from Airways on 16 August 2012)

Products like CAM are predominately en-route sequencing tools providing airlines and controllers with information to enable more efficient use of the airspace. Arrival flow management provides for the optimisation of the arrival sequence to the airport by using the available data to determine the best flow for the traffic mix. This calculation uses such information as the aircraft type and performance, aircraft weight, meteorological conditions and ATC requirements to automatically determine the best arrivals sequence for the runway in use.

In the past airports considered that building more runways was a solution to congestion. The industry is now seeing that flow management maybe the best answer to this ongoing problem.


- Safety

One of the added benefits to flow management has been the increased level of safety. The reduction in airborne holding and vectoring results in a reduction in radio transmissions and the number of tasks to be carried out by both pilots and controllers - this reduces the chance of incorrect information being passed and mistakes being made. Furthermore, the reduced requirement for non-standard procedures removes a level of unnecessary complexity.
Another safety enhancement from automated flow management is the reduced decision making requirement of controllers. Flow management decides the aircraft sequence automatically and therefore the role of the controller moves more towards monitoring aircraft than controlling them. This enables controllers to undertake other tasks to improve efficiency. It is widely recognised that the automation of the sequencing and arrivals process will result in a reduction of errors and improved safety.

- Fuel and CO2 emissions


Reducing fuel costs and CO2 emissions are two of the biggest issues faced by the aviation industry. Qantas announced this year that fuel costs are their biggest cost and the biggest challenge faced in achieving profitability [1]. Uncertainty in oil prices given the political instability in some of the major oil producing nations, especially in the Middle East, has placed considerable pressure on airlines to manage fuel consumption and pricing strategies. Fuel surcharges have been one option explored, however they are largely unpopular with consumers.

Flow management is seen as a good solution as it reduces fuel consumption by reducing the time that aircraft are required to hold either on the ground or in the air. Simply, flow management is good for the airlines as it saves them money. Information from Airways NZ shows that since CAM was introduced in 2008, airlines in New Zealand have saved:

• 20.5 million kgs of fuel
• $29.5 million in fuel costs
• 61.5 million kgs of CO2 emissions

Prior to flow management, airborne delays into Auckland and Wellington during 2007 were on average 28,000 minutes per month. In 2010, the average airborne delays per month had reduced to less than 5000 minutes.

- Efficiency

Reducing delays and increasing the level of reliability benefits all parties involved. Airlines can benefit through lower fuel costs and better on time performance, airports benefit from better runway utilisation resulting in more movements and more money, and the customer benefits from improved reliability and potentially better pricing. As a highly competitive, high cost industry, any cost saving is welcomed.


- Controller ability reduced due to automation

Technology advances and automation are some of the most exciting aspects of aviation. Change is constant. Like any form of automation, one of the risks is that users become too reliant on it [2]. There is a risk that controllers place a greater focus on managing the automated system, rather than controlling the aircraft. This potential issue has been addressed through other forms of automation, such as alerts, however once controllers become too familiar with the system there is concern regarding the ability to cope with a machine failure and unfamiliar tasks.

- Non flow management participants may be penalised

In most situations flow managements systems have been developed to benefit all airlines. However, in Dubai, GE and Emirates have partnered to develop a flow management system that will be used solely be Emirates at Dubai International Airport [3]. This could result in other airlines facing significant delays and increased costs. Flow management maybe available to other airlines in the future, however all media information to date implies that Emirates will gain a priority service from this system.


Flow management is another step in the ongoing automation of aviation and provides a number of benefits. Flow management addresses two of the biggest issues being faced by the aviation industry, congestion and rising fuel costs. While the main drivers for flow management have been to manage these issues, the resulting systems enhance safety and further standardise a complex stage of flight. Automation of flow management is at a relatively early stage, and as systems develop and evolve it there is no doubt there will be an impact on airport and airspace design.


[1] Matt O'sullivan (2012) Rising jet fuel prices weigh heavily on Qantas, retrieved from on 10 August 2012.
[2] V. David Hopkin (1999) Air Traffic Control Automation Embry-Riddle Aeronautical University
[3] GE Aviation and Emirates Airline Work Together to Optimize Traffic Flows, Reduce Flight Costs// (May 22, 2012) retrieved from on 8 August 2012.
CAM information:

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Flow Management
Arrivals Manager
Collaborative Arrivals Manager

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Authors / Editors

Todd Kendall

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