Google’s dream of delivering global internet access with a fleet of balloons floating on the edge of space came to an end on Thursday, as parent company Alphabet disclosed the nine-year project was being closed down.

Loon was one of the most prominent projects from Google’s X lab, the source of other “moonshots” including driverless cars and wind power generated from high-flying kites. It was part of a wave of eye-catching projects that helped to forge Google’s image as Silicon Valley’s most ambitious tech company — though several initiatives have since been shuttered. X was later split from Google to become a subsidiary of parent Alphabet.

Alphabet first claimed success with Loon after a hurricane knocked out communications in Puerto Rico, though it continued to face difficulties with controlling the balloons so that they hovered over the areas where it wanted to provide internet service. Last year, it announced the beginning of the first commercial service for Loon in Kenya, suggesting that technical problems had been ironed out.

However, Astro Teller, head of X, said on Thursday that, “despite the team’s groundbreaking technical achievements over the last nine years, the road to commercial viability has proven much longer and riskier than hoped”. X would not comment on why its view of Loon’s commercial prospects had shifted in the space of the past six months.

Alphabet stuck with its internet balloon project longer than rival Facebook, which had sought to deliver internet service with high-flying gliders. That venture was terminated after one of the giant gliders crashed on landing, underlining the difficulties of managing a fleet of highly fragile craft.

The Loon closure comes less than a year after X’s windpower venture Makani was shuttered.