Alphabet is shutting down Loon, its attempt to deliver internet service via balloons, according to Loon’s CEO.

Loon began in 2011, as an unofficial Google X incubation project, before becoming an official project in 2013. The company’s goal was to use balloons in place of cell towers, to provide internet access to underserved areas. The concept was especially appealing in areas where building cell towers would otherwise be difficult, dangerous or impossible.

The company struck a deal to provide service in Kenya, and was used in disaster zones to help keep people connected, such as in Puerto Rico after Hurricane Maria. Despite its success, however, Alphabet is pulling the plug.

CEO Alastair Westgarth broke the news in a blog post:

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. 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.

Loon was definitely one of the stranger projects to come out of Google and Alphabet and it’s a shame to see it shutting down.