United Airlines has said a technology issue that led to the grounding of flights for a few hours and major delays across its network in the US has been resolved.

“While we expect residual delays, our team is working to restore our normal operations,” the airline said in a statement late on Wednesday.

The issue prompted ground stops at several major United hub airports including Newark, Denver, Houston and Chicago, according to the US Federal Aviation Administration’s (FAA) website.

United said the problem related to its Unimatic system that housed information about each flight that was then fed to other systems, including those that calculated weight and balance and tracked flight times.

The US transportation secretary, Sean Duffy, said on X that the issue was specific to United’s operations and was unrelated to the broader air traffic control system.

United said it was treating the technology issue as a controllable delay, meaning it would pay customer expenses such as hotels where applicable.

As of Wednesday evening, tracking site FlightAware showed that 1,038, or 34%, of United flights had been delayed on Wednesday.

The day’s issues come just a few weeks after Alaska Airlines grounded all of its flights for about three hours due to an IT outage for the second time in just over a year.

In April 2024, Alaska grounded its entire fleet due to an issue with the system that calculates the weight and balance of its planes.