United Airlines Boeing 737 MAX struck by mystery object at 36,000 ft: Is space debris a growing aviation risk?
October 20, 2025
A United Airlines Boeing 737 MAX 8 en route from Denver to Los Angeles was forced to divert and land safely in Salt Lake City on 16 October after its cockpit windshield cracked during cruise flight at around 36,000 feet.
The incident, which left one of the pilots with minor injuries from shattered glass, is now under investigation by the US National Transportation Safety Board (NTSB).
Officials have not yet determined the cause of the impact, and all possibilities remain open from atmospheric debris or hail to a fragment of natural or man-made material falling from above.
While investigators are still collecting data, the case has drawn global attention because of one question that continues to hover over it: could it have been a piece of space debris?
What hit United Airlines as 36,000 feet?
The United Airlines aircraft, carrying 134 passengers and six crew members, experienced a sudden windshield failure while cruising over the Rocky Mountain region.
According to initial reports, the multi-layered glass cracked but maintained structural integrity, allowing the crew to descend and land safely.
United Airlines 737 MAX pilot injured after the windshield cracked at 36,000 while flying from Denver to Los Angeles on Thursday.
— Breaking Aviation News & Videos (@aviationbrk) October 18, 2025
Reports have suggested the possibility of the aircraft being hit by falling space debris or a small meteorite, though this remains unconfirmed.… pic.twitter.com/8qNg6aA0uE
Photographs posted on social media show the right-hand cockpit window crazed with fractures. The object appears to have hit the top corner of the window, shattering both the inner and outer pane and sending glass shards onto the central cockpit controls. In one photo, a pilot shows a bloodied arm. The images are unconfirmed as authentic at this stage.
The captain’s report of a visible incoming object adds an extraordinary twist. At 36,000 feet, few natural phenomena can cause such damage.
Could a bird have shattered the windscreen?
When it comes to making contact with aircraft, birds are often the culprit. But avian risks tend to be higher during takeoff and landing, as not many birds will fly above a few hundred feet.
#Ongoing Past Tuesday (15/11), American Airlines Flight 1855, a B-737, was involved in a bird strike incident in Kansas (US). No injuries reported. On approach, jet struck a flock of geese damaging nose, wing and engine. Updates when possible. pic.twitter.com/HIz9btmbF5
— Air Safety #OTD by Francisco Cunha (@OnDisasters) November 18, 2022
Only one bird species – the Rüppell’s vulture – has ever been recorded at anything like cruising altitudes, and that was over Africa. It holds the world record for highest flying bird, known to be present at altitudes of 11,300 m (37,000 ft) after it collided with a commercial aircraft over Abidjan, Ivory Coast on 29 November 1973.
The impact damaged one of the aircraft’s engines, causing it to shut down, but the plane landed safely without further incident. Sufficient feather remains of the bird were recovered to allow the American Museum of Natural History to make a positive identification of this high-flier, which is rarely seen above 6,000 m (20,000 ft).
So, if not a bird, then perhaps a stray weather balloon? While it’s possible, the relative speed might not be sufficient to produce the kind of impact seen.
The NTSB said it is examining the damaged components and analysing radar, weather, and satellite data to determine whether the impact could be linked to a natural or artificial object. As of now, no evidence has confirmed that space debris was involved.
Meteorologists have noted that severe weather systems and high-altitude hail were present in parts of the region on that day, one of several potential explanations.
However, the possibility of a falling object from space, though statistically remote, has reignited debate over whether the skies above Earth’s air routes are becoming more hazardous as orbital debris increases.
Space debris: A rising risk for commercial flights
Space debris, or “orbital debris,” consists of defunct satellites, rocket stages, and fragments from past launches and collisions.
According to US Space Command, more than 25,000 trackable pieces of debris larger than 10 centimetres orbit Earth, along with millions of smaller fragments.
While most of these objects eventually burn up during re-entry, a significant fraction do not. It is estimated that between 10 and 40% of the mass of large rocket stages can survive and reach Earth’s lower atmosphere. These remnants typically fall into oceans or remote regions, but their precise trajectories are difficult to predict.
The Australian Space Agency is working alongside local authorities in relation to the suspected space debris discovered in the Pilbara region of Western Australia.
— Australian Space Agency (@AusSpaceAgency) October 20, 2025
The debris is likely a propellant tank or pressure vessel from a space launch vehicle.
[More in comments] pic.twitter.com/txm2fByUdl
The European Space Agency (ESA) has warned that uncontrolled re-entries occur almost weekly, with the number expected to rise sharply as thousands of new satellites from megaconstellations such as Starlink, OneWeb and Kuiper are launched.
Each of these re-entries carries a small, but non-zero, risk to aircraft flying below, a concern that was once largely theoretical but is now beginning to intersect with aviation safety discussions.
Rare but not unheard of: Airline incidents involving space debris
There are few confirmed cases of falling space material affecting aviation, but isolated incidents highlight the potential. In 1996, a Chinese passenger jet suffered cockpit damage while flying at around 31,500 feet, believed at the time to have been caused by falling orbital debris, though the link was never conclusively proven.
In 2022, parts of Europe temporarily closed sections of airspace when an uncontrolled Chinese Long March 5B rocket stage was predicted to re-enter over southern Europe. The advisory from the European Union Space Surveillance and Tracking (EUSST) organisation prompted diversions and delays to more than 600 flights across Spain, France, and Italy.
The debris ultimately fell harmlessly into the Pacific Ocean, but the event was a reminder that even low-probability risks can cause large-scale aviation disruption when uncertainty is high.
The ‘unscheduled disassembly’ of a SpaceX Starship in January this year prompted multiple airline diversions, and forced Qantas to delay its planned launch to South Africa. Qantas alleged that that falling SpaceX debris from earlier launches is impacting its operations over “an extensive area of the Southern Indian Ocean”.
How dangerous is space debris to commercial flights?
Scientific modelling is beginning to quantify what was once an abstract hazard. A 2025 study by Wright, Boley and Byers, published in Scientific Reports, analysed decades of orbital and flight path data and found that regions with dense air traffic such as North America, Europe, and South Asia face an annual 0.8% chance of an uncontrolled rocket body re-entry in commercial airspace.
The risk of such a re-entry happening somewhere above major aviation routes globally was calculated at 26% per year. While the probability of an actual aircraft being struck remains extremely small, the researchers concluded that “as launch rates increase, the cumulative exposure of aircraft will continue to rise.”
The study also estimated that over 2,300 rocket bodies are currently orbiting Earth without controlled de-orbit plans, meaning their eventual descent paths cannot be predicted precisely.
These findings align with earlier warnings from the Aerospace Corporation and the Federal Aviation Administration (FAA), both of which have urged for greater coordination between space agencies and aviation regulators on re-entry tracking.
Not all falling objects originate from human activity. Natural meteorites are far more common, though they seldom survive to low altitudes.
A 2020 study in Geology estimated that around 17,000 meteorites fall to Earth each year, most weighing less than 100 grams. Nearly all disintegrate in the upper atmosphere, though a few fragments occasionally reach the surface or, in extremely rare cases, might pass through the cruising altitudes of aircraft.
Even then, the probability of a meteorite striking an aircraft is considered lower than one in a trillion, according to NASA’s Orbital Debris Office. Still, researchers note that meteors enter Earth’s atmosphere at speeds exceeding 11 kilometres per second, meaning that even tiny fragments could cause severe localised damage if one intersected a flight path.
By 2035, 10,000 satellites a year could be falling to earth
The FAA and NTSB maintain established procedures for investigating mid-air impacts and structural failures. Each incident involving a potential external object triggers cross-agency coordination, including consultation with NASA, the US Space Command, and meteorological services.
The FAA’s 2023 risk assessment found that the annual probability of a commercial aircraft downing caused by re-entering debris is less than one in 1.4 billion, but noted that the risk “will increase marginally” as orbital launch rates continue to climb.
Analysts from the FAA and Aerospace Corporation predict that by 2035, as many as 10,000 satellites a year could re-enter Earth’s atmosphere.
Each of these events, though individually low-risk, adds to a cumulative probability that regulators can no longer ignore.
In 2023, the FAA’s own risk assessment projected a 0.0007 annual probability of an “aircraft downing” event caused by falling debris, tiny, but statistically non-zero.
NASA’s updated orbital debris mitigation guidelines require that new spacecraft must be deorbited within 25 years of mission completion.
However, compliance is uneven, and many older rocket bodies remain in orbit with no active control systems.
Experts have repeatedly called for mandatory controlled re-entries and stronger international enforcement. Controlled descents can direct falling hardware into remote ocean regions, reducing uncertainty and minimising airspace disruption.
The world’s skies are becoming more congested in two dimensions — horizontally by aircraft, and vertically by orbital hardware. Global commercial flights have nearly doubled since 2000, while the number of active satellites has grown from around 1,000 to more than 9,000 in the same period.
According to observers, this overlap of domains means that air traffic and space operations can no longer be managed in isolation. Increasingly, aviation safety planners must consider the timing and trajectory of space launches, while space agencies must account for the density of civilian air routes during re-entry windows.
The 2023 Starship test flight that led the FAA to temporarily restrict air traffic over the Gulf of Mexico illustrated how operational boundaries between spaceflight and civil aviation are already overlapping.
United Airlines windscreen incident is under investigation
As of this writing, the NTSB has not confirmed the cause of the United Airlines cockpit damage. Laboratory examination of the windshield and nosecone, along with radar and environmental data, is expected to clarify whether the incident was linked to weather phenomena, a natural meteoroid, or human-made debris.
For now, all such explanations remain speculative. The agency’s final report could take months.
Regardless of the outcome, the incident has highlighted a growing area of concern: the increasingly crowded region between Earth’s atmosphere and near-Earth space, where re-entering hardware and natural fragments occasionally cross the invisible paths of modern air routes.
