For altitudes above 55,000 feet, where no commercial airliners fly, there is currently no air traffic control system.
But traffic management concepts could be coming soon, as a result of the sharp increase in the projected traffic in the coming years. In addition to more frequent rocket launches, plans range from loitering aircraft that would provide communications and other satellite-like services to supersonic and hypersonic passenger planes.
Air traffic management authorities in the U.S. and Europe are considering new ways to coordinate flights at these altitudes. At the German Aerospace Research Center (DLR), researchers this month plan to submit an analysis of tests they conducted with a digital tool designed to avoid potential debris from space flights, part of a larger European project to develop new concepts for high-altitude traffic management. At NASA, researchers have developed software to help operators of loitering high-altitude aircraft self-manage their traffic.
Today, there are relatively few flights of HAPS, short for high-altitude platform stations. These long-endurance, lighter-than-air or fixed-wing aircraft typically fly 8 to 32 kph or 32 to 80 kph, respectively, at altitudes of 60,000 to 80,000 feet, said Russ Van Der Werff, president of HAPS Alliance, an industry advocacy group. He’s also vice president of strategic solutions at Aerostar, which launches 100 to 200 high-altitude balloon and airship flights per year.
Currently, HAPS operators typically notify air traffic controllers ahead of time of their intended ascent or descent path through commercial airspace and coordinate via phone to make sure there are no flight restrictions, Van Der Werff said. HAPS locations and headings are also broadcast via ADS-B Out transponders.
However, he said the high-altitude airspace will need some coordinated traffic management concepts as future flight volumes increase to offer internet, cell phone and emergency communication services.
“There are just so few things up there, it’s practically not been a big day-to-day problem,” Van Der Werff said. “The current system is not as uniform as we’d like or as anyone would like, but it’s also not a high-demand area yet.”
“That’s why we’re trying to build these systems out before it becomes a real problem,” he added.
Future communication networks will require fleets of loitering HAPS over populated areas — 40 to 50 aircraft to cover an area the size of Germany, for example, according to estimates from the European Organisation for the Safety of Air Navigation, or EUROCONTROL, which coordinates air traffic control for Europe.
Increases are predicted in other categories as well. By 2035, the number of supersonic flights from European cities could reach 12,000 per year, according to a “medium scenario” prediction cited by a 2025 European Union Aviation Safety Agency report. Similar 2035 scenarios predict 120 European launches per year for space tourism and other stratospheric balloons, 840 for HAPS and 75 for rockets or spaceplanes.
European concepts
EUROCONTROL hopes to eventually create a comprehensive dashboard view of high-altitude flights it can share with operators, said Dragos Tonea, head of EUROCONTROL’s Integration of New Entrants into Network Operations project, which is developing traffic management concepts for space vehicles, HAPS and supersonic and hypersonic aircraft. This display could also be shared with air traffic controllers overseeing the commercial airspace below, to avoid collisions with any high-altitude aircraft that are ascending or descending.
The idea is to create zones around individual HAPS or fleets that any fast-moving aircraft in the high-altitude airspace would need to fly around, Tonea said. These bubbles would shift as the aircraft within them move, perhaps extending 2,000 feet above and below and 4 km to 8 km around the aircraft, but the parameters are yet to be determined. The rules for collision avoidance within these bubbles would be developed by the operators as an industry, subject to regulator approval, Tonea said.
Supersonic aircraft operators, in contrast, would need to file their flight plans in advance, similar to how today’s commercial aircraft operate. Hypersonic planes could follow prescribed flight corridors, under one option being studied. Transponder location, heading and velocity for aircraft in the high-altitude space would be updated in real time, Tonea said.
To manage future space launches, DLR has developed a mission monitoring digital tool based on software used by FAA for U.S.-based launches, said Lorenz Losensky, a researcher with DLR’s Institute of Flight Guidance. Development began in 2023, funded by the 14 million Euro ($15.9 million) ECHO2 project, EUROCONTROL’s follow-up to the European Concept for Higher Airspace Operation project to develop air traffic management concepts for high-altitude aircraft.
Under the DLR concept, from the time a rocket lifts off to when it exits European airspace several minutes later, the tool would calculate no-fly zones along the rocket’s flight path that all other air traffic would avoid, based on calculated trajectories of where debris could fall if that rocket were to explode, break up or have its stages drop off. Some of these rectangular no-fly zones would be calculated before the launch and displayed on a digital map for specific segments of the flight.
In the case of an accident, the tool would display larger precalculated no-fly zones and notify air traffic controllers to reroute specific commercial flights around the area, Losensky said. The tool would also calculate no-fly zones in real time based on the velocity and heading of the rocket, if it were to break up or veer off its intended path.
DLR tested this tool in February with simulations based on three scenarios: a HyImpulse Technologies rocket launch from SaxaVord Spaceport in the Shetland Islands, Scotland, flying north through U.K. and Iceland airspace; a Dream Chaser-like spaceplane gliding to a runway landing in Italy; and a U.S.-based rocket flying over the Atlantic Ocean and Europe.
For each scenario, DLR engineers introduced accidents where the vehicle broke up midflight, creating falling debris. HyImpulse provided real-time telemetry for the scenarios, and the DLR tool provided a digital map and text and voice communication channels to the testing participants. These included a HyImpulse operator, representatives for regional air traffic control centers along the trajectories and a EUROCONTROL representative, Losensky said.
The testing showed the digital tool would save air traffic controllers time in an emergency, Losensky said, because the precalculated no-fly zones allowed traffic managers to designate ahead of time which commercial flights might need rerouting.
“In a time-critical situation where you maybe have 10 or 15 flights close to the operation, it will be important for the controller to see maybe there are only two or three which you really need to handle technically, and all the others will be safe because they are just going away from the area,” he said.
DLR will report its test findings to ECHO2, which wraps up in December, and EUROCONTROL plans to integrate the DLR tool or a variation of it into its Space Desk for future European launches, Tonea said.
NASA’s tech
For loitering high-altitude aircraft, NASA has developed software that would create a shared perspective among operators. The software provides a digital map, shared communication channels and the ability for operators to share flight plan information and real-time locations and headings with each other so they can project flight paths and anticipate potential conflicts, said Jeff Homola, a researcher at NASA’s Ames Research Center.
“Ultimately, this is what we want to hand off to industry to harden and take forward and innovate on” to help operators manage the airspace themselves, Homola said.
During a two-day simulation in July 2025, NASA demonstrated the software with scenarios involving multiple HAPS operating in close proximity over Florida. In attendance at the airspace operations center at NASA Ames were observers from NASA, FAA and HAPS companies. Two HAPS operators, Aerostar of South Dakota and Sceye of New Mexico, fed data into the simulation from their own operation centers.
“It really makes a huge difference to actually see this stuff play out in real time versus talking about this in the abstract,” Homola said.
Because HAPS are slow to maneuver and greatly influenced by wind currents, their projected trajectories resemble hurricane prediction pathways — probabilistic rather than direct routes between waypoints, said Leonard Bouygues, director of aviation strategy at Sceye. That means operators react with less urgency for a projected airspace conflict between two HAPS than air traffic controllers and pilots would for two passenger airliners projected to cross paths in commercial airspace.
“They’re generally more chill with like: ‘Yeah, I’ll keep an eye out,’” Homola said. “Because if you’re looking out at these time horizons, two hours ahead, a lot changes within that time.”
The work ahead
As for next steps for the DLR digital tool, researchers are considering how to incorporate hypersonic aircraft flights and adding the ability to calculate no-fly zones for multiple launches at once. They’re also planning to launch a sounding rocket outfitted with a transponder to test how they might incorporate space vehicle transponder data or other direct tracking data into the tool’s calculations, Losensky said.
Air traffic managers and operators still have the opportunity to anticipate and build out high-altitude management technologies before they’re actually needed, said NASA’s Homola.
“Right now, it’s not very dense, but the thing that’s driving us to do the research that we’re doing is: You can see that there’s the potential for a lot more in the near future, and trying to get ahead of it,” he said.
