SpaceX's Starlink satellite network was back up and running on Friday as engineers hunted for the root cause of one of its biggest international outages the night before, a rare disruption for the powerful internet system set off by an internal software failure.

According to The Kyiv Independent, the outage affected Ukrainian troops who rely on Starlink terminals, citing a Telegram message from the military saying Starlink is down across the entire front. The military now says its connections are back online after going down for about 150 minutes, “the longest in the war.”

A brief outage of Starlink, Elon Musk’s satellite internet service, impacted Ukraine’s front line military communications, just hours after Russian drones hit the city of Kharkiv. CNN’s Nick Paton Walsh reports from Kyiv.