United Airlines is revealing what caused a nationwide stoppage on Tuesday, impacting hundreds of flights on a busy travel day coming out of the long Labor Day weekend.
The airline initially said a "systemwide technology issue" was responsible for grounding flights for more than an hour.
United later elaborated to say that a software update triggered a glitch, forcing it to request that the FAA halt all of its departures across the country, according to the Associated Press.
The airline added that it was not a cybersecurity issue.
The pause was put in place around 1 p.m. ET and was lifted shortly before 2 p.m. after the issue was resolved.
More than 350 United flights were delayed, and seven were canceled.
The brief outage drew responses from Transportation Secretary Pete Buttigieg and Rep. Eric Swalwell -- who was on a United flight himself when the delays were announced.
Buttigieg said his department will "make sure" United Airlines meets its obligations to passengers affected by the ground stop.