United Airlines resumes operations after widespread tech system error stops flights

United Airlines resumed operations after it was forced to temporarily ground all of its mainline flights on Wednesday evening due to a technical issue.

"We are working with customers to get them to their destinations after a technology disruption on Wednesday evening," United Airlines wrote in a post on its Instagram story. "The underlying technology issue has been resolved, and, while we expect residual delays, our team is working to restore our normal operations."

Mainline flights are operated directly by United, using its own aircraft and crew. These typically include Boeing 737, 757, 767, 777, and 787 jets, as well as Airbus A319 and A320 models.

Transportation Secretary Sean Duffy said Wednesday night that he was briefed by United CEO Scott Kirby and that the technical issue was "specific to United's operations" and was "unrelated to the broader air traffic control system."

SPIRIT AIRLINES TO FURLOUGH 270 PILOTS DUE AMID LOWER OFF-SEASON DEMAND

On Wednesday evening, a spokesperson told FOX Business that a "technology issue" forced the airline to halt all mainline flights. 

United apologized for the disruption in a statement posted on social media as the glitch was ongoing, and said its teams were working to resolve the issue as quickly as possible.

In response to a concerned traveler on social media, United acknowledged the issue and thanked the passenger for their patience. 

"We're aware of the system error at this time and are working on a fix to have you on your way as soon as possible," United responded. "We understand that this disruption has caused frustrations during your travel and appreciate your continued patience."

UNITED AIRLINES, JETBLUE PARTNERSHIP GETS TRUMP ADMIN CLEARANCE TO FLY

Despite the airline's efforts, passengers around the world felt the ramifications of the glitch.

One passenger in Denver told Fox News Senior Correspondent Aishah Hasnie that she had been stuck on a United plane on the tarmac in Denver for nearly two hours.

COURT ALLOWS WOMEN TO SUE QATAR AIRWAYS OVER ALLEGED STRIP SEARCHES

None of the gates were available, and the pilot told the passenger there was no update on when those on board could get off the aircraft.

The passenger also said some planes have been sitting for twice as long as they had been waiting.

CLICK HERE TO READ MORE ON FOX BUSINESS

Fox News Digital's Bradford Betz contributed to this report.