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

The Federal Aviation Administration issued a ground stop alert after being requested by the carrier due to a technological problem.

The airline identified the affected system as “Unimatic,” which stores key information about each flight and relays it to other systems. This includes data necessary for calculating weight, balance, and tracking flight times.

In response to the situation, the airline categorized it as a “controllable delay,” thereby covering customer expenses such as accommodation and meals when 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 shared on X that he was briefed by United CEO Scott Kirby. He confirmed the issue was “specific to United’s operations and unrelated to the broader air traffic control system.”

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

“We are assisting customers to reach their destinations following a technology disruption on Wednesday evening. The core technology issue has been resolved. Although some residual delays are anticipated, our team is diligently working to resume normal operations.”

United Airlines spokesperson

An airline spokesperson informed Nexstar’s KDVR in an earlier statement that United had grounded its mainline flights, which are the larger aircraft operating under the main carrier’s name. They mentioned that delays might continue into the evening but assured that customer safety and reaching their destinations remain their priority.

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.