Severe convective weather has become an increasing challenge for the European aviation network in recent years, with the component of air traffic flow management (ATFM) delays attributed to weather now the second-largest delay category after air traffic control constraints.
EUROCONTROL’s new Aviation Trends paper shows how the EUROCONTROL Network Manager (NM) is working closely with all operational stakeholders to mitigate, with growing success, the negative impacts of capacity bottlenecks, adverse weather and network instability on airlines, airports and air navigation service providers (ANSPs) through the application of CWBO, a new set of Capacity and Weather-Based Operations procedures.
CWBO combines meteorological forecasts, real-time updates and expected traffic demand to identify emerging capacity shortfalls, including those caused by convective weather affecting en-route operations.
The process relies on close coordination between EUROCONTROL’s Network Manager Operations Centre (NMOC) and ANSPs, airports, airlines and meteorological service providers, and is used by the NMOC to manage air traffic flows in predefined circumstances – due to severe convective weather, turbulence, staff shortages, or congestion in certain parts of Europe.
First introduced in Summer 2025 in response to the all-time high of weather-based delays recorded in Summer 2024, CWBO proved immediately effective in reducing network unpredictability during disruptive days by limiting last minute changes, preventing delays from spreading across Europe, and helping airlines and airports plan more reliably.
When demand is expected to exceed capacity beyond predefined thresholds, CWBO is applied following a trigger system. To the three triggers introduced to initiate this procedure in 2025 (Manage severe weather; Manage significant weather accompanied by capacity reductions in the area; and Manage capacity shortages in a coordinated way), in 2026 CWBO was expanded to add a fourth trigger to tackle instances of emerging network instability – defined as when delays in a specific airspace become critical; when total European ATFM delay approaches the defined critical instability threshold of 80K minutes of delay in the network; or approaching 20K minutes of delay in a single area control centre.
Our Aviation Trends paper finds that the application of CWBO in 2025 and 2026 has made a significant impact towards strengthening the tactical resilience of the European aviation network by:
- saving around 3.1 million delay minutes already this year (1 May-31 August), well over triple the delay saving in 2025 (1 May-15 October) of 900K delay minutes
- delivering around €400 million in actual cost savings for operational actors in 2026, taking an average ATFM delay cost of €130 per minute (vs around €117 million in 2025)
- raising network stability by 14% on challenging days featuring weather and capacity bottlenecks
- improving the network’s adaptability, responsiveness and decision-making, minimising uncontrolled mass reroutings, and preventing reactionary delays.