Air Traffic Management and Operations

Single European Sky

There were 9.6 million flights to or from EU28+EFTA airports during 2017, and they are forecasted to increase by 42% between 2017 and 2040 under the base traffic forecast. The Single European Sky (SES) initiative [51] has introduced regulatory instruments at the EU level to help address the environmental challenges associated with this expected growth.

Performance Scheme

The SES ‘Performance Scheme’ [52], [53] defines key performance indicators and sets mandatory local and EU targets in the fields of environment, safety, efficiency and capacity, while taking into account their interdependencies. The scheme captures the relationship between flight routing and environmental impacts through two Key Performance Indicators (KPIs). These involve measuring horizontal flight efficiency by comparing the great circle (shortest) distance against (1) the trajectory in the last filed flight plan (KEP) and (2) the actual trajectory flown (KEA). These KPIs are regarded as reasonable proxy measures of Air Navigation Service Provider efficiency.

Considering the complexity of the route structure, interface procedures and air traffic control operations, horizontal en route flight efficiency is not considered an appropriate performance indicator for the airport and terminal manoeuvring area. Instead, the additional taxi-out time and the additional transit time in the Arrival Sequencing and Metering Area (ASMA)11 is monitored against an unimpeded time based on periods of low traffic demand. Likewise, in order to measure the performance of aircraft ground operations at airports, the actual taxi-out time of a flight is compared to an unimpeded taxi-out time during periods of low traffic demand. At present, the performance scheme does not cover non-CO2 emissions, vertical flight efficiency, noise levels or air quality.

The European Commission is currently conducting a review of the Performance and Air Traffic Management (ATM) Charging Schemes which is due to be completed by the start of 2020. This will in particular respond to the findings of the recent European Court of Auditors report [54], and better capture the responsiveness of the ATM System to requests for preferred flight trajectories of airspace users.

Network Manager

The European Commission nominated EUROCONTROL as Network Manager in July 2011 until the end of 2019 [55], [56]. The SES Network Manager coordinates between operational stakeholders to effectively manage imbalances between capacity and demand, and thereby optimise the performance of the European aviation network. The aim is to prevent congestion in the air through the design, planning and management of the European ATM network and to limit unnecessary fuel burn and emissions through flow and capacity management.

Single European Sky ATM Research (SESAR)

SESAR is the technological pillar of the Single European Sky [57] funded by the European Union, EUROCONTROL and industry partners, with a total budget of €2.1 billion for the original SESAR programme (2008-2016) and €1.6 billion for the SESAR 2020 programme (2014-2024). It aims to improve ATM performance by modernising and harmonising systems through the definition, development, validation and deployment of innovative technological and operational solutions. These solutions are defined in the European ATM Master Plan, along with required operational changes and a roadmap for their implementation. The solutions are developed and validated by the SESAR Joint Undertaking (SJU), and deployed through ‘Common Projects’ supported by dedicated SESAR deployment governance and incentive mechanisms. All of these processes actively involve the stakeholders and the Commission in different forms of partnerships.

The implementation of the deployment framework [58] will allow SESAR to fully deliver its environmental benefits from concept to implementation. The European Union has contributed €1.5 billion from the Connecting Europe Facility Programme to support operational stakeholders in this process.


11 ASMA is measured as a cylinder of airspace centred on the airport with a radius of 40 nautical miles.

Excess CO2 emissions due to network flight inefficiency

When comparing the gate-to-gate actual trajectories of all European flights in 2017 against their unimpeded trajectories12, there is an additional 5.8% gate-to-gate CO2 emissions at European level. Figure 4.1 illustrates the average excess CO2 emissions per flight broken down into the different flight phases. The average excess CO2 emissions has remained stable over the last 6 years, even though traffic has increased.

It should be noted, however, that there are a number of reasons why the actual trajectory flown can vary from the unimpeded trajectory, and therefore 100% efficiency is not achievable (e.g. due to adverse weather, avoidance of ‘Danger Areas’, need to maintain minimum separation, lack of capacity leading to diversions, avoidance of relatively high route charges). Some inefficiency is unrecoverable due to necessary operational constraints and interdependencies [59].

The 2018 European ATM Master Plan [60] ambition is to continue reducing the additional gate-to-gate flight time and additional gate-to-gate CO2 emissions to reach 3.2% and 2.3% respectively by 2035.


12 Unimpeded trajectories are characterised by: zero additional taxi-out time, no level-off during climb (full fuel CCO), no sub-optimal cruise level, en route actual distance equal to great circle distance, no level-off during descent (full fuel CDO), no additional time in the Arrival Sequencing and Metering Area (ASMA), zero additional taxi-in time.

Environmental performance and targets

Horizontal en route flight efficiency

The total additional distance flown in 2017 within the SES area was 222.8 million kilometres, which resulted in approximately 3 million tonnes of additional CO2 emissions. The SES Performance Scheme includes two binding targets at the EU level for 2019 set at 4.1% for the en route flight inefficiency of the last filed flight plan (KEP) and 2.6% for the actual trajectory (KEA).

Figure 4.2 shows that KEA decreased to 2.81% and is on track to reach the target by 2019. This is largely due to the simplification of the airway structure in the en route airspace, thereby moving towards a free route airspace (see Section 4.4). KEP decreased from 4.91% in 2016 to 4.73% in 2017. This improvement was due to better flight planning and the reduction of unnecessary route restrictions (e.g. military areas). It is expected that most of the European airspace would have implemented free route airspace by 2019. Consequently, there may be limited scope for further reduction beyond the 2.6% target.

Airport operational efficiency

While the average additional Arrival Sequencing and Metering Area (ASMA) time is about 1.24 minutes per arrival in 2017, significant variations can be seen at an airport level (Figure 4.3). In 2017, inefficiencies in the arrival flow at the top 30 airports resulted in 8.33 million minutes of additional ASMA time. The main contributor being London Heathrow, which accounted for 23% of the total minutes, while its traffic share was less than 6%. This is a consequence of the mode of operations at Heathrow, which prioritises full use of runway capacity.

In comparison to the additional ASMA time, the average additional taxi-out time per departure improved slightly at the 30 busiest airports in the SES area from 3.82 minutes in 2016 to 3.77 minutes in 2017, with some variation at an airport level (Figure 4.4). Waiting in a queue for take-off generates unnecessary CO2 emissions and unpredictability.

The implementation of departure manager, in combination with the integration of Airport Collaborative Decision Making (A-CDM) systems, aims to improve the departure sequencing. This provides optimised taxi-time, and improves predictability of take-off times, by monitoring surface traffic. However, this effect is not always fully visible as some A-CDM implemented airports (Figure 4.9) show similar taxi-out performance as non A-CDM airports. Arrival Management (AMAN) now extends into en route airspace as far as 180-200 nautical miles from the arrival airport, and should support better traffic sequencing.

Figure 4.513 illustrates the trend over time of the average additional ASMA and taxi-out times for the busiest airports in the SES area. Note that the sets of airports changed between the 2012-2014 and 2015-2017 periods, and are therefore presented separately.


13 The disconnect in the trend line is due to a change in criteria for ‘ASMA’ airports between Reference Period 1 (RP1 - 2012 to 2014) and Reference Period 2 (RP2 - 2015 to 2019).

Operational initiatives

Free Route Airspace

Free Route Airspace is defined as that airspace within which users may freely plan a route between any defined entry and exit point, subject to airspace availability. Figure 4.6 provides an overview of Free Route Airspace (FRA) and direct routing implementation in Europe as of the end of 2018. It fosters the implementation of shorter routes and more efficient use of the European airspace. The proportion of flight time flown in Free Route Airspace during 2017 was 20% compared to 8.5% in 2014. Since 2016, it should also be noted that cross‑border free route activities have been implemented in Estonia, Latvia, Italy, Malta, Slovenia and Croatia. The Network Manager estimates 2.6 million tonnes CO2 savings from the implementation of FRA since 2014.

Continuous Climb Operations / Continuous Descent Operations

In 2015, harmonised definitions, metrics and parameters to measure Continuous Climb Operations (CCO) and Continuous Descent Operations (CDO) in Europe were agreed by a Task Force of European ATM Stakeholders. These included the definition of a ‘noise CCO/CDO’ and of a ‘fuel CCO/CDO’. The fuel CCO/CDO measures the vertical flight efficiency, in terms of fuel and CO2, for the entire climb and descent profile respectively. The noise CCO/CDO measures the vertical flight profile efficiency to 10,500 ft for CCO and from 7,500 ft for CDO, which are the phases of flight where the primary impact is considered to be noise.

A European-wide study [62] of current CCO/CDO implementation, based upon the agreed definitions, was subsequently performed in 2017 where flights with level segments (a proxy for inefficiencies in the climb and descent phases of flight) were measured and their fuel burn, CO2 and financial impact estimated.

Figure 4.7 and Figure 4.8 use a sliding scale to indicate the average amount of time flown in level flight for both the noise and the fuel CCO/CDO at selected European airports in 2017. The scales for the noise and fuel CCO/CDOs are different, based on minimum, average and maximum values, illustrating the relative performance between the airports. Note that the average amount of level flight flown on departure (noise CCO) is relatively low at 5 seconds compared to 67 seconds for arrivals (CDO).

Within the scope of the fuel CCO and CDO definition, the average amount of level flight flown by all European flights is 44 seconds for departures (CCO) and 165 seconds for arrivals (CDO). Figure 4.8 shows that there is there is a relatively high amount of level flight within the European core area, indicating a link between CCO/CDO and airspace complexity.

The results indicate a greater potential to reduce noise and fuel use during descent (CDO) compared to climb-out (CCO), and overall the room for improvement is less in the noise CCO/CDO compared to the fuel CCO/CDO. The ability to perform CCO/CDO profiles also appears to be linked to airspace complexity rather than airport capacity. The results also indicate that a typical flight with level segments could benefit on average from CO2 savings of up to 48 kg for a CCO and 145 kg for a CDO, reflecting the higher CO2 penalties caused by inefficiencies in the descent phase. The potential CO2 benefits from optimising European wide CDOs were estimated to be ten times more than those of optimising CCOs. Furthermore, there is a much smaller potential to optimise the noise CCO/CDO compared to the fuel CCO/CDO. Acknowledging that the optimisation of environmental benefits depends upon local conditions, it was concluded that CCO/ CDO implementation should, where possible, focus on the optimisation of the flight profile from top of descent.

The total potential savings in Europe is up to 350,000 tonnes of fuel, which is equivalent to 1.1 million tonnes of CO2 emissions per year. However, it should be noted that the ability to fly 100% CCO or CDO may not be possible for a number of reasons such as safety (i.e. time or distance separation), weather or capacity.

Implementation of Airport Collaborative Decision Making

Airport Collaborative Decision Making (A-CDM) aims at improving the overall efficiency of airport operations, especially on aircraft turn-round and pre-departure sequencing processes.

Increased predictability can be of significant benefit for all major airport and network operations by improving flow management and sector planning. This is achieved by the Network Manager receiving more accurate target take-off times from the airport. On average, the implementation of A-CDM enables a reduced taxi time of 1 to 3 minutes per departure [63].

A further 16 airports (Figure 4.9) have implemented A-CDM since 2016, resulting in 40.9% of European departures operating from a A-CDM airport. The 2016 A-CDM impact assessment report [64] identified savings generated from 13 of the 17 A-CDM airports that have demonstrated tangible taxi-time performance improvements of 108,072 tonnes of CO2 emissions.

Additional operational initiatives

Further solutions which are expected to provide substantial environmental savings are highlighted in Table 4.1.

Stakeholder actions

Air Navigation Service Providers
Austro Control has developed and implemented radio navigation procedures to reduce both noise and emissions at Salzburg airport. The airport is located on the northern edge of the Alps, and airlines generally prefer to approach from the south, stay high and descend to a reasonable approach altitude of around 5,000 ft after being clear of mountains. This was followed by an ILS approach from the north, as long as wind conditions allow. This flight extension of approximately 46 km results in additional fuel burn, gaseous emissions and noise over densely populated areas. In order to reduce these impacts, Austro Control has developed a direct approach procedure from the south that enables airlines to safely descend through the valley even in poor weather (IMC) conditions.

Airline Operators

2. Austrian Airlines case study: Crew Transport by Train
Alongside the transportation of passengers using classic intermodal travel situations, Austrian Airlines is now cooperating with the Austrian Federal Railway Company (ÖBB) to transport cockpit- and cabin-crews to work. Each month ÖBB receives the number of required seats on specific trains from Austrian Airlines and puts in place the respective seat reservations. Austrian Airlines incorporates the train details into the crew duty roster. As well as reducing costs and CO2 emissions, the crew experience a more comfortable and flexible journey compared to road shuttle services.

3. IAG case study: Flying the fuel efficiency flag
Aviation fuel typically comprises 25% or more of airline costs and accounts for over 97% of airline CO2 emissions, so focusing on fuel efficiency makes both commercial and environmental sense. IAG has set ambitious targets to improve fuel efficiency by 10% in 2020 compared to 2014, thereby achieving an average fuel efficiency of 87.3 gCO2 per passenger kilometre.

Big wins have come from new aircraft such as the Boeing 787 and the Airbus A350 / A320neo that deliver up to 20% better fuel efficiency compared to the aircraft they replace. However, small measures also add up, including weight reduction, regular maintenance and optimizing flight operations. During 2017, IAG’s flight carbon efficiency improved by 2.6% versus 2016, which saved over 80,000 tonnes of CO2 through more than 25 separate fuel efficiency initiatives including using electric push back tugs, reduced engines for taxiing and reducing aircraft drag by reducing the time when landing lights are extended into the airflow.

During 2017 IAG also began implementing the Honeywell ‘GoDirect’ fuel efficiency software. This will enable mining of big data to identify further fuel efficiencies, and will allow IAG to benchmark fuel use across its fleet and share best practice among the Group’s five airlines. IAG’s focus is now on developing innovative ways to communicate fuel efficiency information to flight crews in a way that engages and inspires them to change behaviour and minimize excess emissions.