SES environmental performance and targets

The SES Performance Scheme Reference Periods (RP) are divided into five year periods. This report captures the results of RP2 and the start of RP3, while highlighting intentions for the remainder of RP3 and RP4.

Reference periods

In 2019, the SES Performance Review Body (PRB) Annual Monitoring Report [7]  highlighted the challenges imposed upon the ATM system due to the traffic growth of 11.8 % during RP2 according to the STATFOR forecast. This led to significant increases in delays, particularly in the summer periods of 2018 and 2019, and consequently the SES Performance Scheme environmental targets were not reached. Consequently, the PRB recommended that structural issues in the ATM system should be addressed and that the Network Manager (NM) should work with ANSPs and Member States to improve re-routing proposals and minimise route restrictions, as well as support more closely the implementation of Free Route Airspace and Flexible Use of Airspace [8] .

Following the dramatic reduction of traffic beginning in 2020, it was expected that the environmental performance of the ATM system would improve significantly due to reductions in capacity constraints. However, while the target for the Horizontal En-route Flight Efficiency KPI was met in 2020, the magnitude of improvement from 2.95% to 2.51% was limited in view of the significant traffic reduction. Furthermore, the PRB observed that several Member States did not achieve their environment targets despite experiencing very low traffic, suggesting that the KPI reflecting the relationship between flight routing and environmental impact may need to be re-evaluated. It should be noted that other environmental performance indicators were able to capture the performance improvement from more direct routeings and optimised vertical flight efficiency (see section 5.3).

In light of the European Green Deal, a more ambitious and holistic approach when applying the Performance Scheme appears necessary. Improvements should be based upon an assessment of the interrelatedness between the Performance Scheme, existing market- based measures, as well as future regulatory measures which are currently under discussion within the EU institutions. On-going work is currently considering new performance indicators for RP4 that more closely correlate with actual CO2 emissions and, where possible, using metrics based solely upon ANSP performance.

The total additional distance flown in 2019 (RP2) within the SES area was 256 million kilometres, which resulted in approximately 3.5 million tonnes of additional CO2 emissions. In comparison, an additional 120 million kilometres was flown in 202140 (RP3) leading to approximately 1.6 million tonnes of additional CO2. The SES Performance Scheme includes one binding target at the EU level for the entire 2022-2024 period that is set at a maximum of 2.4% for the en-route flight inefficiency of the actual trajectory (KEA). The last filed flight plan inefficiency indicator (KEP) is no longer being used beyond 2020 as the focus is on the more tactical KEA indicator.

Figure 5.1. shows that KEA decreased to 2.51% in 2020 and increased to 2.59% in 2021. Following Brexit, these figures no longer include UK data as the UK is no longer subject to the SES Performance Scheme. In order to take into account the COVID pandemic, the KEA targets for 2021 and 2022 were subsequently revised taking into account existing circumstances [9] , while the targets for years 2023 and 2024 were maintained on the basis of the expected recovery. The decrease in KEA across the network in 2020 can largely be explained by the removal of around 1,200 network restrictions (both horizontal and vertical) during the pandemic measures together with more efficient direct routings [10] . As traffic increased in 2021, several of these constraints were reinstated in order to maintain both safety and capacity.

As traffic starts to return to pre-COVID levels, the challenge will now be to maintain these efficiency improvements promoting ‘green’ recovery principles such as more dynamic use of airspace constraints [10]  that are applied only at times and traffic conditions in which they are fully justified.

40Although the UK was not participating in the SES Performance Scheme in RP3 (2021) the numbers are shown for comparative purposes. In 2021, without the UK, the additional distance flown was 110 million kilometres.

The Performance Scheme includes various indicators that are only monitored at either EU-level or local level with no binding targets. Two of these indicators are highlighted below for the top 40 airports in terms of flight movements across the Network, including the UK.

The average additional Arrival Sequencing and Metering Area (ASMA) time, which measures the delay in the arrival flow of air traffic, for the top 40 airports remained fairly constant from 2014 to 2019 at around 2.0 minutes per arrival (range of 1.91-2.04 mins), but decreased significantly to 1.22 minutes in 2020 and 0.92 minutes in 2021 ( Figure 5.2. ).

It should be noted that the ASMA indicator is currently subject to consultation based on stakeholder feedback. This exercise includes a potential revision of the Taxi-out time and the development of a Taxi-in time indicator.

All airports experienced a reduction in ASMA time from 2019 to 2020, although significant variations can be observed at an airport level ( Figure 5.3. ). Arrival flow inefficiencies at the top 40 airports resulted in 1.9 million minutes of additional ASMA time and approximately 0.3 million tonnes of additional CO2 emissions, down from a peak of 9.2 million minutes in 2019. Likewise, the average additional taxi-out time per departure almost halved between 2019 (3.9 minutes) and 2020 (2.0 minutes) due to the lower traffic levels. This reduction continued in 2021 (1.9 minutes).

Fuel burn per flight can be broken down across flight stages. SES Performance Scheme data has been used to compare the gate-to-gate actual trajectories of all European flights every year up to 2020 against their unimpeded trajectories41. Figure 5.4. provides the average excess CO2 emissions per flight, broken down into different flight phases. While this is not an official indicator within the SES Performance Scheme, it does highlight that 75% of excess fuel burn originates from the en-route horizontal / vertical inefficiency as well as horizontal inefficiency during arrival (ASMA).

This figure also demonstrates that although traffic decreases were significant in 2020, there are still constraints that prevent the optimal unimpeded trajectory from being flown. It should be noted that 100% efficiency may not be achievable due to various reasons (e.g. adverse weather, avoidance of ‘Danger Areas’, non-standard events, diversions etc.). It should be understood that the shortest route, as described by the optimum unimpeded trajectory, does not necessarily equal the most environmentally optimal route as other factors such as winds need to be considered.

It should be noted that the calculation of the excess CO2 emissions based on SES performance Scheme data is no longer supported by EUROCONTROL, and from 2021 the focus will be on measuring gate to gate fuel burn and CO2 emissions by using the NM excess fuel burn indicator (see section 5.3).

41Unimpeded 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 (as weather influences are excluded), no level-off during descent (full fuel CDO), no additional time in the Arrival Sequencing and Metering Area (ASMA), zero additional taxi-in time.