A United Airlines emergency landing likely caused by collision with a weather balloon

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A United Airlines plane appears to have collided with a weather balloon while cruising over Utah at 36,000 feet last week, fracturing layers of its windshield and forcing an emergency landing.

A California company called Windborne Systems said it started looking into the situation Sunday, not long after the National Transportation Safety Board said it was investigating. Windborne quickly concluded that the Boeing 737 Max very likely ran into one of its balloons, despite the company's best efforts to prevent such collisions.

The plane, which was flying from Denver to Los Angeles, did not lose cabin pressure and landed safely in Salt Lake City last Thursday. United said 134 passengers and six crew members were aboard.

Windborne CEO John Dean said he was surprised at the extent of the damage to the plane's windshield because Windborne's balloons weigh only 2.4 pounds at takeoff with a simple bag of sand serving as ballast. The impact sent fragments of glass flying in the cockpit.

The company said it follows all Federal Aviation Administration rules for the size and design of its balloons that gather data to help improve weather forecasts.

“I find this extremely concerning, and unacceptable in the case of a collision, regardless of what the official regulations are, It resulted in injury to a pilot, which I’m simply not okay with whatsoever,” Dean said in a post on X.

The airline referred questions to the NTSB, which isn’t responding during the current government shutdown. The NTSB statement didn't mention any injuries.

Dean said in an email Tuesday that data about the location of the flight lined up closely with the last known location and altitude of one of the company's balloons before it stopped transmitting right around the reported time of the collision. Windborne forwarded all of its data to the NTSB, which will ultimately determine what happened.

Windborne has launched more than 4,000 balloons, and the company said it coordinates with the FAA each time, filing notices for pilots and sharing live updates on balloon positions with the FAA.

The company said it has already tweaked the software for its balloons to minimize the time they spend between 30,000 feet and 40,000 feet. It's also looking at different ballast designs to reduce the force of any future collisions and minimize the potential for damage or injuries.

NTSB investigators will release a preliminary report in a few weeks, but the full report might not come for more than a year.