Several air traffic control centres (ACCs) faced traffic increases that were significantly higher than the European average – in particular in the south-east of Europe, which was affected by changing traffic patterns as a result of Russia’s full-scale invasion of Ukraine, as well as by geopolitical tensions in the Middle East. These included Tirana ACC (Albania), which was 20% busier than 2023, Rome ACC (Italy, +18%), Zagreb ACC (Croatia, +12%), Prague ACC (Czech Republic, +11%), Padua ACC (Italy, +11%), Belgrade ACC (Serbia & Montenegro, +10%), Bratislava ACC (Slovakia, +10%) and Ljubljana ACC (Slovenia, +10%). In a number of cases, these traffic levels were higher than expected/planned for, and also resulted in traffic levels well in excess of pre-pandemic levels.
When the number of aircraft due to arrive at an airport, or to pass through a specific air traffic control sector, exceeds the available capacity as declared by the relevant airport/air navigation service provider (ANSP), the EUROCONTROL Network Manager will, in order to maintain safety, sequence the traffic by issuing a departure slot, delaying some flights on the ground – an Air Traffic Flow Management (ATFM) delay.
ATFM delays for the core summer months of June to August 2024 were 16.9 million minutes, an average of 5.4 minutes per flight, which was 41% above 2023. July was particularly challenging, with ATFM delays of 6.5 minutes per flight
There was a combination of factors for these high levels of delay: structural capacity shortfalls, unexpected traffic growth in parts of the network, significant convective weather (thunderstorms, etc.), less airspace available for re-routings due to the war in Ukraine, increased military activity, exceptional sickness levels in one ANSP, and a lack of adherence to the planned vertical levels in flight plans.
The weather-related ATFM delay per flight (2.2min/flight) was 41% more than in 2023. For safety reasons, aircraft avoid convective weather, reducing the number of aircraft flying through the affected airspace. As flights try to re-route into non-weather-affected areas, there is a knock-on effect when these other areas are already operating in a saturated environment at the limit of their capacity – resulting in additional ATC capacity delays.
ATC capacity delays (where issues are known about in advance) accounted for 1.9 minutes per flight, 82% more than 2023. Here the significant traffic increase in key parts of the network, such as the south-east axis, has been a major factor; some of this increase was not forecasted. 7 ANSPs produced 85% of the ATC capacity delays between 1 June and 31 August:
- DFS (Germany): 16%
- HungaroControl (Hungary): 16%
- ENAIRE (Spain): 16%
- DSNA (France): 12%
- ENAV (Italy): 11%
- Croatia Control (Croatia): 9%
- HASP (Greece): 6%
Some ANSPs have not delivered the agreed capacity and the EUROCONTROL Network Manager is actively working with them on urgently needed improvements. Other ANSPs have performed robustly, in some cases delivering more capacity than originally planned.
ATC Staffing, where there are fewer staff available on the day than planned, amounted to 0.6 minutes per flight in June, broadly comparable with 2023 and slightly lower than in 2019.
Delays, as experienced by the passenger, are composed of reactionary (knock-on) delays, airline scheduling delays and delays on the ground – as well as ATFM delays. Overall arrival punctuality for the three months was 65%, slightly worse than in 2023 (66%). These figures, which indicate the proportion of aircraft arriving no more than 15 minutes behind schedule, reflect the rise in traffic and the increased impact of adverse weather and ATC capacity restrictions.
Increasing weather-related delays have been an area of particular focus this summer. We are seeing better cross-border collaboration, but significant improvements are still required; a more network-oriented approach to weather management needs to be adopted and implemented by summer 2025.
Other areas of focus for the EUROCONTROL Network Manager, such as scheduling and the prioritisation of the first rotation (to reduce knock-on delays for the rest of the day), have seen improvements. Airports in the network have focused on reducing average ground delay, with an improvement in performance over the three months of close to 7%. For the airlines, there has been a 24% improvement in scheduling (compared to June/July/August 2023) and a 12% improvement in first rotation performance.
In contrast, there has been a marked worsening of vertical flight plan adherence. During the summer 2024 period almost 600,000 flights did not adhere to the planned vertical levels of their flight plan, which is around 60% more than in 2023. This has a very negative double impact on ATC capacity, as the airspace capacity made available for these aircraft is not used and is therefore lost. The aircraft intrude on other airspace and use capacity that was not planned for them, resulting in ANSPs cutting declared capacity levels in order to safely handle the greater unpredictability.
An improvement in vertical flight plan adherence is clearly required and this will be a key area of focus in summer 2025.
Performance during July and August demonstrates that there is an urgent need to introduce further structural improvements in preparation for summer 2025 and beyond, as regards:
- the Network Operations Planning Process (in particular, enhancing forecasting using earlier sharing of airline schedules)
- Capacity delivery according to plan
- Flight plan adherence
- a more network-focused approach to weather management.
There is also a clear, urgent and growing requirement to recruit and train more controllers to support an increase of capacity.
The EUROCONTROL Network Manager will continue to work intensively with all aviation stakeholders on improving the performance of the European aviation network – and to ensure that passengers get to their destinations safely and with the least possible delay.
