Space debris is a growing problem, and not just in Earth orbit.

Once a week, on average, a spacecraft (or part of one) falls back into Earth’s atmosphere; most of these objects are empty rocket stages, but some are dead satellites whose low orbits finally decayed enough for them to slip into the atmosphere. They’re basically like human-made meteors, but most of them don’t survive long. This is because of the heat and shredding force that come with high-speed collisions with the air. However, some bits of debris from the objects can exist long enough to plummet through the sky, ranging from dust-mote-sized particles to whole propellant tanks. And this can be a big problem.

There’s a risk one of those stray pieces can hit a passing aircraft — that risk is small, but it’s growing enough that experts are now trying to figure out how to reduce it.

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space debris are falling back into Earth’s atmosphere with increasing regularity. And as satellite constellations and general spacecraft operations continue to become more common, the risk of deorbiting space debris will only go up.

There’s a 26% chance that sometime in the coming year, space debris will fall through some of the world’s busiest airspace during an uncontrolled re-entry, according to a paper published early in 2025 by researchers at the University of British Columbia. The odds of that debris actually striking an aircraft (or vice versa) are small but measurable: By 2030, the chances of any given commercial flight hitting a piece of falling space debris could be around 1 in 1,000, according to a 2020 study.

Those odds don’t sound terribly daunting if you’re the gambling type, but given the number of planes crisscrossing the friendly skies at any given moment, that’s a lot of rolls of the dice. And it’s a high-stakes gamble; risk includes not just the likelihood of an event, but the potential outcome (hundreds of people dead, in this case of that 2020 study). That’s partly because commercial aircraft carry so many passengers, but it’s also because it takes a much smaller bit of debris to cause a catastrophe in the air than on the ground, especially where jet engines are concerned.

“Aircraft can be affected by much smaller pieces of debris. For example, airplanes flying through the ash of a volcano is risky because of the small particles,” European Space Agency space debris system engineer Benjamin Virgili Bastida told Space.com. “Kind of a similar thing could happen with re-entering debris.” Virgili Bastida and his colleagues recently published a paper in the Journal of Space Safety Engineering outlining the challenges of deciding when and where to close airspace for falling space debris.

Long March 5B rocket re-entered Earth’s atmosphere. It was the fourth time a Long March 5B had made an uncontrolled re-entry, and this time its ground track passed over Spain, prompting a flurry of airspace closures.

The Long March rocket was an unusual problem even by space debris standards; the roughly 20-ton core stage was much, much more massive than most spacecraft and rocket parts that drop back into the atmosphere (and China is no longer using that version of the rocket now that the final modules of its Tiangong space station are in orbit). China’s space agency also wasn’t very forthcoming about the rocket’s track or the fact that it was going to re-enter the atmosphere at all. But despite being an anomaly, the Long March incident is also a good illustration of both the potential danger and the need for more specific warnings, rather than broad ones.

Despite a few other close calls and airspace closures in recent years — like a SpaceX spacecraft that re-entered over European airspace in the summer of 2025, prompting airspace closures — we’ve been lucky so far. But maintaining that streak, without causing air-traffic gridlock by closing too much airspace for too little reason, is going to require a lot of work on multiple fronts.

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“What we are trying to investigate in the studies we are running is to see what is really the threshold for risk for an aircraft,” said Virgili Bastida. “At what risk should we react?”

Other pieces of the puzzle include limiting the amount of debris that even makes it to the altitudes where most planes fly (around 30,000 to 40,000 feet or 9,144 to 12,192 meters), more accurately predicting where and when spacecraft will re-enter, and coordinating between space agencies and air traffic controllers to make the decision-making progress less clunky. And none of that is as easy as it sounds.

Blue Origin, among others — to develop narrower, more specific airspace closures for rocket launches. Those efforts are likely to apply to dealing with the other end of spaceflight, returning debris, as well.

To get there, space agencies and air traffic controllers need two key types of information. First, when and where will the spacecraft hit the atmosphere? How much of it will survive intact down to 40,000 feet? Exactly what part of the sky will that debris be falling through (and when)?

Second, how big a threat is that debris to a passing aircraft? That answer depends on the size, speed and features of the aircraft, and researchers are in the process of working out models that can offer more specific answers. It will then be up to space agencies and air traffic controllers, working together, to decide when the risk is high enough to close a patch of sky — and for how long.

“If we react at every risk, half of the world will be impacted every now and then, so it’s not feasible,” said Virgili Bastida. “Do we react for everything which has a chance to reach the ground? Or do we react only for the very large objects, as we did for the Long March?”

Agencies in charge of aviation and air traffic control in individual countries (like the FAA in the U.S. and the Civil Aviation Administration of China in China) will eventually have to define how much risk requires them to close airspace for falling space debris. That could include factors like the likely size of the pieces and the chances of an impact, so a standard might look something like, “If there’s a 1 in 3,720 chance of particulate matter getting sucked into a jet engine, we should close the airspace.” (Those numbers are just for illustration.)

Satellites don’t spend much time passing through this rarefied region, and most of them are already dead and in the process of being disintegrated by the friction of the thin air against their hulls.

“There is very little information on this region of the atmosphere, so the models are just kind of extrapolated down or up,” said Virgili Bastida.

Building better models requires more data, and one way of getting that data is ESA’s upcoming DRACO (Destructive Re-entry Assessment Container Objective) mission. When it launches in late 2027, DRACO will measure — in 200 sensors’ worth of detail — exactly how a small satellite disintegrates during its plunge into Earth’s upper atmosphere. Its goal is to measure not just the spacecraft’s trajectory on the way down, but exactly when different components burn or break apart.

To do that, DRACO’s lead system engineer Alex Rosenbaum and his team are fitting the DRACO capsule with components in a range of different materials, each outfitted with sensors to measure its temperature and the time and altitude of its fiery demise. There will even be a mock-up of a propulsion bay and a composite fuel tank, even though DRACO won’t actually have working propulsion. The capsule itself won’t survive, which is the point. A black box, similar to the flight data recorders used on commercial aircraft, will escape the high-altitude breakup via parachute.

“It is a very peculiar mission because it will be very short,” Rosenbaum told Space.com. “We are working for several years on a mission that will be operative for a couple of hours.”

Meanwhile, there’s the Inter-Agency Space Debris Coordination Committee — a group of 13 space agencies whose members include JAXA, ESA, Roscosmos, CNSA and ISRO. IADC runs an annual exercise called a Re-Entry Campaign, in which members choose “an interesting test case” from among the defunct satellites due to drop back into Earth’s atmosphere in the coming months. Member agencies pool their information on the object and their predictions about the time and path of its re-entry. Afterward, they compare what actually happened to their predictions in order to help test and refine those models. It’s steady work with cumulative results — not too dramatic but very important.

The Re-Entry Campaigns and DRACO will help improve predictions and shed light on how to reduce the amount of space debris by designing satellites and rocket stages that disintegrate as completely as possible at high altitudes. But once space agencies and air traffic controllers have that data, someone is going to have to decide what to do with it.

What exactly does that look like?