What happened
On October 16, 2025, at 0643 MDT, a United Airlines Boeing 737-8, registration N17327, was performing a scheduled domestic passenger flight from Denver International Airport to Los Angeles International Airport. While cruising at a pressure altitude of 36,000 feet near Moab, Utah, the aircraft experienced a midair collision with an object.
The captain reported seeing an object on the horizon before a loud bang and a significant impact occurred on the first officer's forward windshield. The impact shattered glass, resulting in 1 minor injury to the captain, who sustained superficial lacerations to his arm. The other 111 occupants were not injured.
Following the impact, the crew initiated a descent and diverted the flight to Salt Lake City International Airport. During the descent, the crew noted that the first officer's window overheat light had illuminated. The aircraft landed at SLC without further incident and was met by airport rescue and firefighting vehicles.
The investigation
Investigators examined the aircraft's flight data and cockpit voice recorder, which indicated the airplane was traveling southwest at 233 degrees magnetic with a groundspeed of 395 knots at the time of the collision.
Data regarding aerial objects in the area was reviewed. WindBorne Systems Inc. reported losing contact with a global sounding balloon (GSB) in the vicinity of the aircraft during the timeframe of the accident. The GSB, an unmanned high-altitude platform, had been launched from Spokane, Washington, on October 15, 2025. The balloon's last communication occurred between 0636 and 0643 MDT, reporting a pressure altitude of approximately 35,936 feet.
The damaged windshield, a PPG Aerospace model, was removed and sent to the NTSB Materials Lab for examination. The component featured a multi-layered construction including thermally tempered glass panes, conductive heating films, and urethane and vinyl interlayers.
Findings
- The aircraft's track was nearly the reciprocal of the weather balloon's track.
- The GSB system, consisting of a lightweight envelope, avionics, and a silica ballast system, was designed to minimize harm upon impact.
- A Notice to Airman for the balloon launch operations had expired on October 15, 2025.