(Bloomberg) -- A U.S. safety agency is investigating anaccident involving a massive experimental drone Facebook Inc.is developing to bring the internet to remote areas of theworld.

No one was hurt in the incident, which came during the unmannedaircraft’s first test flight on June 28. It marks the latest hiccupin Facebook’s plans to wirelessly connect the world, following anexplosion earlier this year that destroyed one of its satellitesand political resistance to the service in India.

The high-altitude drone, which has a wingspan wider than aBoeing Co. 737 and is powered by four electric engines, suffered a“structural failure” as it was coming in for a landing, accordingto a previously undisclosed investigation by the NationalTransportation Safety Board.

“We were happy with the successful first test flight and wereable to verify several performance models and components includingaerodynamics, batteries, control systems and crew training, with nomajor unexpected results,” the company said in an emailedstatement.

While there has been no previous mention of the NTSBinvestigation or details about the incident, the company did saythe drone, called Aquila, had had a structural failure in a July 21web post.

(YouTube: Aquila's First Flight)

‘Substantial’ damage

The accident occurred at 7:43 a.m. local time near Yuma, PeterKnudson, an NTSB spokesman, said. The NTSB has classified thefailure as an accident, meaning the damage was “substantial.” Therewas no damage on the ground, Knudson said.

The flying wing designed to eventually be solar powered so itcan remain aloft for long stretches. The social-media company isseeking to boost the percent of people around the world who connectto the internet by leapfrogging ground-based infrastructurelimitations.

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Company Chief Executive Officer Mark Zuckerberg said he was"deeply disappointed" when a SpaceX rocket explosion Sept. 1 destroyed aFacebook satellite that would have helped spread internet accessacross Africa.

The company has also had political hurdles. In India, forexample, Zuckerberg was surprised when people rejected thecompany’s offer of free web services that had Facebook at thecenter. Locals saw it as a poorly-disguised land grab of the Indianinternet market, instead of a charitable project.

Interest in Indonesia

Indonesian Vice President Jusuf Kalla spoke to Zuckerberg in recentdays at the Asia-Pacific Economic Cooperation summit in Peru aboutusing the Aquila drone to beam internet to remote parts of thecountry, the Jakarta Post reported.

"If we make the right investments now, we can connect billionsof people in the next decade and lead the way for our generation todo great things," Zuckerberg said in a Facebook post from thesummit on Saturday.

Zuckerberg was so excited about the drone aircraft’s firstflight that he flew to the test facility in Arizona early on June28, according to an account in The Verge.

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In a web post after the flight, he said it was so successful itwas extended from 30 to 96 minutes. “We gathered lots of data aboutour models and the aircraft structure — and after two years ofdevelopment, it was emotional to see Aquila actually get off theground,” Zuckerberg wrote.

The accident was the second involving an unmanned aircraftdesigned to fly for long periods as a less expensive alternative tosatellites. An Alphabet Inc. drone known as the Solara 50 wasdestroyed May 1, 2015, at a desert landing strip in New Mexicoafter experiencing control problems as it flew in a thermalupdraft, according to the NTSB.

Carbon fiber

The aircraft are made with the latest carbon-fiber technology in anattempt to make them as light as possible so they can stay aloftwith minimum power.

Facebook’s drone has a wingspan of 141 feet (43 meters) andweighs 900 pounds (408 kilograms). It has no traditional fuselageand is built almost entirely of thin, black wings. It flies slowly,using only the energy required to power three hair driers,according to Facebook.

Aquila is designed to fly for months at a time, using solarenergy to replenish batteries at altitudes above 60,000 feet(18,288 meters). It will be equipped with a laser communicationssystem that can deliver data 10 times faster than currenttechnologies, Facebook said in a promotional video.

The NTSB hasn’t yet released any of its preliminary findings onthe extent of the damage or the potential causes of thefailure.

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