WindBorne Weather Balloon Payload Impacts United 737

After the flight crew of a United Airlines Boeing 737 Max reported a cracked windshield and glass particles hitting them on October 16, speculation arose that it may have been caused by impact with falling space debris. However, weather balloon company WindBorne has acknowledged that the foreign object debris (FOD) event, which occurred at FL360, likely was caused by one of its balloons and payloads.

According to a WindBorne blog post, “We learned about UA1093 and the potential that it was related to one of our balloons at 11 p.m. PT on Sunday (October 19) and immediately looked into it. At 6 a.m. PT October 20, we sent our preliminary investigation to both NTSB and FAA, and are working with both of them to investigate further.”

The company added, “We believe that the FOD was likely a WindBorne balloon…We are grateful that to our knowledge there were no serious injuries and no loss of pressurization. The flight, which was en route from Denver to Los Angeles, diverted to Salt Lake City. The plane itself later flew to Chicago.”

Weather balloons and their payloads are “designed to be safe in the event of a midair collision,” according to WindBorne. “This is the purpose of the FAA Part 101 and ICAO weight limits. Our balloon is 2.4 pounds at launch and gets lighter throughout flight.”

The company added, “We are working closely with the FAA on this matter. We immediately rolled out changes to minimize time spent between 30,000 and 40,000 feet. These changes are already live with immediate effect. Additionally, we are further accelerating our plans to use live flight data to autonomously avoid planes, even if the planes are at a non-standard altitude. We are also actively working on new hardware designs to further reduce impact force magnitude and concentration.”

These balloons are typically not equipped with any kind of air traffic control signaling device, but they do transit Class A airspace from FL180 to FL600. This airspace requires that aircraft be equipped with a transponder that meets FAA technical standard order (TSO) specifications and that the aircraft also have ADS-B Out equipment.

In any case, the applicable FAA regulations—Part 101—do not require any electronic signaling device capability for uncrewed free balloons. Limitations of these balloons are spelled out in 101.1 (payload limits of 4, 6, or 12 pounds, depending on various factors, impact force for rope or suspension devices, etc.).

Transponder and ADS-B equipment manufacturer uAvionix makes extremely small and lightweight transponders, some of which are installed in high-altitude balloons, according to chief commercial officer Christian Ramsey. The ping200X, for example, can deliver Mode S transponder and ADS-B Out signals, all in a package that weighs just 50 grams. The price is $4,800.

“We have a lot of high-altitude balloon customers,” he told AIN. “The issue is that these aircraft transit Class A airspace, and the current equipage requirements for that airspace is a full TSO transponder.”

In comments to the FAA’s proposed Part 108 beyond-visual-line-of-sight regulations for uncrewed aircraft systems, uAvionix wrote: “The rule should harmonize the equipage requirements between crewed and uncrewed aircraft transiting Class A and operating in Upper Class E airspace [above FL600].

“This approach aligns with the FAA’s Upper Class E Traffic Management operations above FL600 and directly reflects FAA Reauthorization Act of 2024 §361. This section directs the FAA to establish a framework for high-altitude balloons for continuous tracking/identification and position reporting, integration with existing NAS users, and timely rulemaking to enable safe civil and public operations at high altitude. Codifying 1090ES ADS-B Out as the cooperative conspicuity standard for these operations implements that congressional direction while keeping spectrum impact minimal, given the very low traffic volumes and planned profiles at these altitudes.”