The drone with which Facebook hopes to provide internet to much of the world had a structural failure during its first test flight and is now under investigation by the National Transportation Safety Board, Bloomberg reported today. Facebook offered few details about the structural failure, which took place as the drone was coming in for a landing. An NTSB report on the incident is expected within “a month or two,” the agency told The Verge.

On July 21st, I reported that Facebook had successfully completed the first test flight of Aquila, the drone with which it hopes to someday provide internet to much of the world. My account, which was based on interviews with Mark Zuckerberg and members of the team that was present on the ground for the June 28th flight, presented the flight as an unqualified success.

The aircraft’s failure was noted in passing in the eighth paragraph of Facebook’s engineering blog on the day our story was posted. (“We are still analyzing the results of the extended test, including a structural failure we experienced just before landing.”)

No one was injured as a result of the failure, and there was no damage to the ground, the NTSB said. But the aircraft was “substantially damaged,” a spokesman said. An aircraft is considered substantially damaged when it is no longer airworthy.

Facebook declined to offer more details, citing the ongoing investigation. It has previously said that its test flights are designed to stress-tests the drones and that it expects there to be failures like this along the way. But it is unclear why Facebook did not disclose the NTSB investigation or the fact that the drone was substantially damaged during multiple interviews with its CEO and its team.

For my part, I failed to note the significance of the line in its blog post afterward. As a result, my Aquila story was incomplete, and painted too rosy a picture of the company’s adventures in aerospace. I now regret not asking about the details of the drone’s landing — though when Facebook told me it “successfully” completed a test flight, that seemed to preclude the possibility of Aquila becoming substantially damaged in flight. The next time Facebook crows about a success, that’s worth keeping in mind.

We’re updating our original post about Aquila’s test flight with a link to this article.