The National Transportation Safety Board (NTSB) has released its preliminary report on the United Airlines Boeing 737 high-altitude collision incident over Utah last month, concluding that the aircraft most likely collided with a commercial weather balloon.

The impact caused considerable damage to the cockpit’s windshield, showering the pilots with glass before the aircraft safely diverted to Salt Lake City. The captain sustained lacerations to his right arm following the collision, which was initially thought to be caused by space debris.

United Airlines 737 Struck Weather Balloon At High Altitude

Last month, Simple Flying reported on an incident involving a United Boeing 737 MAX 8 colliding with high-altitude debris over the skies of Utah. On October 16, United Flight 1093 departed Denver (DEN) en route to Los Angeles (LAX) and was at cruising altitude near Moab, Utah when it struck an object midair. According to the NTSB, the captain « noticed an object distant on the horizon » while the aircraft was cruising at 36,000 feet.

However, before he could even mention the object to the first officer, the 737 collided with the object, causing a « loud bang » and shards of glass to enter the cockpit. During its investigation, the NTSB discovered that California-based weather balloon developer, WindBorne Systems, had lost contact with a high-altitude global sounding balloon (GSB) launched from Spokane, Washington, a day earlier. Radar tracking revealed that the GSB was in the vicinity of the United jet’s flight path when the impact occurred.

As per the NTSB report,

« The GSB was launched from Spokane, Washington at 1129 MDT on October 15, 2025. The balloon traveled south from Washington, down through Oregon and Nevada before turning northeast, and was crossing though Utah at the time of the accident. »

Incident Could Have Been « Devastating »

NTSB Chair Jennifer Homendy commented that the midair collision « could have been really devastating for the aircraft and those on board. » While only the captain sustained injuries during the incident, damage occurring elsewhere on the aircraft could have precipitated a tragedy. Cabin pressurization remained stable after the impact, while the first officer’s window overheat light turned on at one point.

According to Windborne Systems, its GSBs are deliberately designed to minimize damage in the event of collisions like last month. The company does not use any large metal or high-stiffness structures, with the balloon envelope and ballast container made of a thin plastic film and silica. The company also said it has implemented changes to prevent such incidents from occurring again. This includes improving air traffic alerts, minimizing time spent in commercial airspace, and further reducing GSB weight to minimize possible damage from impacts.

Aircraft windshields are designed with multiple layers to withstand the rigors of flying, which includes impact events like bird strikes. The NTSB notes that they are certified to withstand an impact with a four-pound bird without penetration, as well as having non-splintering internal panes. The windshield installed on United’s 737 MAX was manufactured by PPG Aerospace and consists of « a thermally tempered glass pane, a conductive heating film for deice capabilities, a urethane interlayer, a vinyl interlayer, a urethane interlayer, and a thermally tempered glass pane. »

Aircraft Remains Grounded A Month Later

Looking at data from Flightradar24, the aircraft involved in this incident — a two-year-old United 737 MAX 8 (registration: N17327) — has not re-entered service more than a month after the collision. After diverting to Salt Lake City (SLC) following the midair collision, the aircraft conducted a brief flight to Chicago Rockford (RFD) on October 19 and has not flown again.

According to the NTSB’s report, the damaged windshield was removed from the aircraft and sent to the NTSB Materials Lab in Washington, DC, to be examined. Simple Flying has reached out to United Airlines for comment and will update this story accordingly.