DENVER (KDVR) — Commercial airline United Airlines ordered a ground stop for flights at multiple major airports Wednesday evening.

According to the ground stop alert posted by the Federal Aviation Administration, the carrier had asked for the ground stop to be issued due to a technology issue.

The airline said the impacted system is called “Unimatic,” and houses information about each flight that is fed to other systems. The information shared includes those that calculate weight, balance and track flight times.

The airline said it is treating the matter as a “controllable delay,” which means the airline paid for customer expenses such as hotels or meals where applicable.

The airline also shared that the outage began at 5:12 p.m. MDT and was resolved within a few hours.

Transportation Secretary Sean Duffy said in a post on X that he had been briefed by United CEO Scott Kirby and learned the issue was “specific to United’s operations, and is unrelated to the broader air traffic control system.”

The airline provided the following update at about 8:15 p.m. MDT:

“We are working with customers to get them to their destinations after a technology disruption on Wednesday evening. The underlying technology issue has been resolved, and, while we expect residual delays, our team is working to restore our normal operations.”

United Airlines spokesperson

A spokesperson for the airline told Nexstar’s KDVR in a statement earlier in the evening that United had grounded its mainline flights – larger planes that operate under the main carrier’s name. The statement went on to say that delays were expected to stretch into the evening, but United vowed to keep their customers safe and work to “get them to their destinations.”

The FAA said in a statement that it had “offered full support to help address their flight backlog.”

Impacted air traffic controller facilities included Los Angeles, Salt Lake City, Chicago, Washington, D.C., Denver, and other U.S. facilities, but were also impacting facilities in Canada, according to the FAA ground stop.

In San Francisco, the ground stop was lifted and flights had resumed as of 6:20 p.m PDT, an SFO spokesperson told Nexstar’s KRON.

By 7 p.m. MDT at Denver International Airport, however, there were 412 delays and 10 cancelled flights. Of those delays, 176 were attributed to United Airlines.

United said the outage was unrelated to concerns about cybersecurity in the airline industry.