Google has shut down its Loon project, which hoped to make giant helium balloons an alternative to cell towers in remote areas of the world.

Alphabet Inc, Google’s parent company, said Loon is not commercially viable, nearly ten years after it was launched to bring the internet to rural areas where building cell towers is too expensive or too difficult due to lack of roads.

Loon aimed to bring connectivity to remote areas hard to reach, using high-altitude helium balloons.

“While we’ve found a number of willing partners along the way, we haven’t found a way to get the costs low enough to build a long-term, sustainable business,” Loon CEO Alastair Westgarth wrote in a blog post.

“Developing radical new technology is inherently risky, but that doesn’t make breaking this news any easier. Today, I’m sad to share that Loon will be winding down.”

But Westgarth insisted the project should be remembered for some achievements.

“We found ways to safely fly a lighter-than-air vehicle for hundreds of days in the stratosphere to anywhere in the world,” Westgarth said.

“We built a system for quickly and reliably launching a vehicle size of a tennis court, and we built a global supply chain for an entirely new technology and business.”

Last year, Loon launched a pilot project in Kenya to provide a 4G network to nearly a 31,000-square-mile area, but the project reportedly ran out of funds.