By Clarence Oxford SpaceWar
A new study from the University of British Columbia (UBC) has found that there is a 26 percent chance each year that debris from space rockets will re-enter Earth’s atmosphere and pass through an area of high air traffic density.
Although the probability of such debris striking an aircraft remains low, the findings underscore the growing risk of space junk disrupting flights and imposing financial burdens on airlines and passengers.
Disruptions caused by space debris are not unprecedented. In 2022, aviation authorities in Spain and France were forced to temporarily close parts of their airspace due to the uncontrolled re-entry of a 20-tonne rocket segment. With an increasing number of both rocket launches and commercial flights, UBC researchers stress the urgent need for policy action.
“The recent explosion of a SpaceX Starship shortly after launch illustrated the challenges of closing airspace at short notice,” said lead author Ewan Wright, a doctoral candidate in interdisciplinary studies at UBC. “Authorities established a no-fly zone, forcing multiple aircraft to reroute or return to their origins. That incident involved known debris locations, whereas uncontrolled re-entries from orbit offer far less predictability.”
When rockets launch satellites into orbit, substantial rocket segments often remain in space. If these discarded stages reside in low Earth orbit, they can re-enter the atmosphere unpredictably. While most of the material burns up during descent, sizable fragments can survive and fall toward the surface.
Growing Air Traffic and Unchecked Re-Entries
The researchers examined flight activity on the busiest day of 2023 and correlated it with the likelihood of rocket debris re-entry, using a decade of historical data. Denver, Colorado, had the highest air traffic density that day, averaging one aircraft per 18 square kilometers.
By assessing various air traffic density thresholds, the study determined that regions experiencing at least 10 percent of Denver’s peak air traffic-such as the Vancouver-Seattle corridor-face a 26 percent annual likelihood of debris re-entering their airspace.
“The southern European airspace closure in 2022 occurred in an area with just five percent of peak air traffic density,” Wright noted. “Globally, the chance of re-entry into such moderately busy regions stands at 75 percent per year.”
In 2024, there were 258 successful rocket launches, with a record 120 cases of uncontrolled rocket debris re-entering Earth’s atmosphere. More than 2,300 rocket bodies remain in orbit, while airline passenger numbers are projected to grow nearly seven percent in 2025, according to the International Air Transport Association.
Space Industry Transferring Risks to Airlines
The study also estimated the probability of rocket debris colliding with an aircraft at one in 430,000 per year.
When debris enters high-traffic airspace, aviation authorities must choose between maintaining normal flight operations or closing airspace to mitigate potential risks. “But why should these authorities have to make such choices? Uncontrolled rocket re-entries are a consequence of design choices, not an inevitability,” said co-author Dr. Aaron Boley, an associate professor in UBC’s physics and astronomy department. “The space industry is, in effect, shifting its risks onto airlines and passengers.”
A more sustainable approach, the researchers argue, would involve rockets designed for controlled atmospheric re-entry, ensuring they land harmlessly in designated oceanic zones. However, implementing such solutions requires international cooperation. “Countries and private firms won’t invest in improved rocket designs unless regulations mandate it for all,” said co-author Dr. Michael Byers, a professor of political science at UBC. “Governments must collaborate to establish new global standards.”
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