For a decade, the UK has measured the environmental efficiency of its airspace.
European air traffic management is a patchwork that entangles progress toward streamlined operations. During growth periods, when ideas emerge about how to improve the handling of aircraft trajectories, the uneven structure creates hurdles. In downturns, the lack of flexibility has prevented resources from being better allocated. During severe crises, such as Russia's invasion of Ukraine, the distribution of responsibilities further complicates the situation.
Although reaching the goal of a single European sky remains far off, there have been advances. Short-term crises are being managed, and the industry is pursuing implementation of more efficient, harmonized tools and procedures for the longer term.
- Industry is concerned about traffic volatility
- Free-route airspace is becoming the norm
Among the major players in the air traffic management (ATM) sector are Eurocontrol—the organization in charge of ATM in Europe, extending to Turkey—and national air navigation service providers (ANSP).
The war in Ukraine has affected the aviation network significantly. The drastic increase in military operations is creating pressure on Eurocontrol as the network manager, which translates into delays, notes Eduardo Garcia, manager of European ATM coordination and safety at the Civil Air Navigation Services Organization (CANSO), the industry’s trade association. “With NATO, we are looking for ways to mitigate the impact on civil operations,” he says.
In Germany, NATO has activated three flight corridors that cross the country at different flight levels, points out Urs Lauener, chief operating officer of Swiss ANSP Skyguide. “Civil traffic is prohibited in those corridors, which impacts capacity,” he says. “Moreover, Russia has to be circumnavigated. To relieve the control center in Karlsruhe, Germany, we have taken over some traffic.”
Poland, too, has had to manage more traffic. Improved performance at the Reims en route control center, operated by French ANSP DSNA, has enabled the center to take over some of that traffic and relieve Polish control centers. Meanwhile, some countries, such as Finland, have lost traffic.
Overall, ATM remains seriously complicated for Ukraine’s neighbors, due in part to the lack of predictability.
Last year’s surge in passenger traffic may have been a consequence of the regained freedom and opportunity to spend money after the lifting of COVID-19 pandemic restrictions, Lauener suggests. But that effect may not last. “The money was spent, inflation has emerged, and sustainability is coming to the forefront of passengers’ concerns,” he says.
Executives at France’s DSNA worry about the availability of human resources. “A low point was touched in 2021, partly because of a policy allowing the replacement of only 50% of the civil servants leaving on retirement,” Chief Operating Officer Guillaume Blandel says. To meet growing needs, a hiring plan is being implemented, with a 4-5-year training cycle.
“More flexibility would be appreciated, as it would enable [us] to easily move controllers from one center to another, depending on the needs,” Blandel adds. “The 6-7-a.m. slot at [Paris Orly Airport] usually sees 25 departures, but a staff reduction, to 13 from 15 controllers, is about to prevent some of the departures from taking place.”
Skyguide is poised to experiment with a potential solution. “For each sector, controllers have to know so many details by heart that this limits their ability to work in different sectors,” Lauener says. “Typically, they have to know that handing over to the Aix-en-Provence control center [in France] has to take place at Flight Level 240. In the future, the system will supply that information so that controllers will be able to perform their job independently from the location.” Skyguide is implementing the concept at its virtual control center, scheduled to be operational in 2024.
Many in the industry say the timing is ideal for recasting ATM. “We are at a critical moment,” Garcia says. “Traffic is growing, and new entrants are expected such as [electric vertical-takeoff-and-landing vehicles] and supersonic transport aircraft.”
The height of the pandemic provided a useful time for spurring long-term thinking. “Before COVID, we were experiencing strong growth and could see pinch points starting to appear across the network,” says Chris Norsworthy, director of airspace and future operations at UK ANSP NATS. “With reduced traffic, we could improve efficiency with less pressure and explore more options for improvement.”
Traffic has since grown, and NATS is operating at 88-90% of pre-pandemic traffic levels, according to Norsworthy.
Has sustainability displaced capacity as a priority? “There are complex relationships between sustainability and capacity, and it’s right that sustainability issues have continued to gain prominence,” Norsworthy says. “Back in 2012, we developed a pioneering metric, known as 3Di, to measure the environmental efficiency of UK airspace, even though we are still regulated against a capacity metric.” The 3Di metric is used to compare an aircraft’s actual flightpath to the most efficient possibility.
Use of a continuous descent cuts fuel consumption and shrinks the noise footprint, thanks to the elimination of power-setting changes. The proportion of continuous descent operations (CDO) can be improved, Blandel notes. “Satellite navigation can help, as well as strengthened relations between control centers,” he says. “The idea is to make the airspace more dynamic. The status of a military area—active or inactive—can be factored in. Methods may change depending on the time of day, when traffic is more or less intense.”
As required by CDO procedures, letting the flight management system optimize the trajectory requires a cultural change. “Controllers were trained to devise the shortest routes possible,” Blandel explains. CDOs account for about 30% of operations in France, and the goal is 50% for 2025-26 to meet a European standard, he notes.
To encourage the use of sustainable aviation fuel (SAF), a principle similar to the “best-equipped, best-served” rule could be created. Eurocontrol uses that rule as an incentive to fit higher-accuracy navigation systems on aircraft. Doing the same with SAF may follow soon, Blandel suggests.
Environmental improvements sometimes are technically possible but tricky to implement when they may modify an existing equilibrium. A new procedure around an airport may curtail CO2 locally by 5% and reduce the number of overflown residents by 10,000. But if that total is the result of subtracting 15,000 people from one area but adding 5,000 elsewhere, the newly overflown people would be so vocal that making the change becomes a political issue, Blandel says.
Typically, new Required Navigation Performance-Authorization Required satellite-based approach procedures, as were deployed at Ajaccio Airport on Corsica, could be used at other locations, but those changes often are impeded by such political considerations.
DSNA has at least been happy with 4-Flight, an en route management system it developed with Thales that enables more direct trajectories. The system not only has an intrinsic capability by providing more accurate forecasts of 4D trajectories—3D in space plus time—but its use also eases cross-border coordination.
In addition, 4-Flight has a positive effect on capacity. A 10% increase has been seen in higher airspaces compared to 2019 levels, Blandel says.
Free-route airspace—a concept under which flight crews choose their preferred routes in a relaxed framework—gradually is becoming the norm. It has been implemented in France for two years, and the plan is to grow its adoption until 2025. “We are implementing free-route airspace one control center after the other, taking into account training needs for the new 4-Flight system,” Blandel says. “We worked a lot with our military counterparts.”
“Airlines know what’s best for a flight depending on the route, weather, load factor and aircraft performance,” Skyguide’s Lauener says. Among the tools enabling free-route airspace is controller-pilot data link communications.
In the UK, further free-route airspace is planned to be deployed on March 23 over the southwest. It could save an annual 12,000 metric tons of CO2, Norsworthy says. Free-route airspace typically starts at about 24,000 ft. “In the future, we will explore options to bring this down further,” he adds.
Along the same lines, NATS wants to “systemize” the lower airspace to reduce intervention—and so workload—for controllers and pilots. “Thanks to technologies and procedures such as performance-based navigation, crews would be much closer to a ‘file-it, fly-it’ experience [with their flight plan],” Norsworthy says. “This also enables greater accuracy across the network.”
A new system may be used soon to advance both safety and capacity. Automatic dependent surveillance-contract (ADS-C) is at the trials stage. “It enables the controller to get live, firsthand information from the cockpit,” Lauener says. Determination of the accurate top-of-descent point improves flight-trajectory predictability for the controller. In turn, capacity is increased. Moreover, the controller may detect a potential conflict and require another aircraft to slow down early, avoiding holding patterns. ADS-C will be mandatory by the end of the decade.
Overall, controllers may expect automation to revolutionize their jobs, just as it has revolutionized cockpits, in Lauener’s view. “Controllers will monitor the system,” he says. “Therefore, they may need 2-3 days of simulation training every month to maintain the required skills in case the system fails and they have to understand the situation and solve it.”
