LONDON — When the European Union introduced its own satellite navigation program, it billed the service as more robust, precise and reliable than GPS — and a way to end the bloc’s reliance on the system controlled by the United States military.

But most of the European navigation system, known as Galileo, has been out of use since Thursday — the latest mishap to befall the program since it began running in a pilot phase in late 2016.

The episodes have raised questions over whether new satellite launches in the Galileo program, which the European Commission said would be fully operational by 2020, should be paused until experts find the cause of the failures.

Galileo is available free to anyone around the world, and the European Union says that around 100 million smartphones are capable of receiving its signals. Users are unlikely to have noticed the outage because phones and other devices are programmed to use Galileo in conjunction with other services such as GPS, Russia’s Glonass system and China’s Beidou.