United Airlines was recovering Thursday from a technology problem Wednesday afternoon that temporarily grounded all of its flights and caused widespread delays, as well as some flight cancellations.

A nationwide technical glitch f0r United Airlines Wednesday led to massive headaches for travelers coast to coast, and over 1,000 delayed flights. At SFO, according to flight data examined by the Chronicle, more than 150 flights were delayed leaving the airport, seven were canceled, and around 136 inbound flights were delayed as well.

Seventeen more flights leaving SFO were reportedly cancelled Thursday morning.

Flights were temporarily grounded at United's hubs in Newark, Denver, Houston, San Francisco, and Chicago while the issue was being resolved, which led to the rash of delays. NBC Bay Area reports that the ground stop at SFO lasted two hours.

United initially did not make any public comment about what caused Wednesday's troubles, but Reuters reports that the airline was treating it as a "controllable delay" and would be paying customers' expenses for hotels, etc.

The airline has since confirmed, per Reuters, that the trouble was with "its Unimatic system that houses information about each flight that is then fed to other systems, including those that calculate weight and balance and track flight times."

Transportation Secretary Sean Duffy went on Xitter Wednesday night to note that the problem was unrelated to broader issues with air traffic control staffing around the country, and was specific to United's operations.

Similar ground stops, like one that impacted Alaska Airlines in April 2024, have been prompted by problems with software that calculates the weight of planes for takeoff. Alaska also had a systemwide ground stop last month that lasted several hours due to an unexplained "IT outage."

United Airlines issued a statement saying, "While we expect residual delays, our team is working to restore our normal operations."

Photo by David Syphers