United Airlines flight delays accumulated across the country on Wednesday as a widespread technical failure led the airline to cancel all of its mainline flights. The technical failure, which was due to dispatch and fuel system issues, caused over 800 flights to be cancelled and left thousands of travelers stranded in the country and internationally.

The carrier clarified that its mainline flights — large aircraft like the Boeing 737, 757, 767, 777, and 787, and the Airbus A319 and A320 families — were included. Regional partner carrier flights were excluded from the grounding directive.

"Because of a technical problem, we're grounding United mainline flights at their point of origin," a United representative said to FOX Business. "We anticipate further evening flight delays as we work through the problem."

FAA Confirms United Airlines Requested National Ground Stop

The Federal Aviation Administration confirmed it ordered the ground stop on behalf of United Airlines so the airline could have time to fix the outage.

United Airlines requested the FAA to suspend temporarily its flights nationwide as they resolved a technology issue," the FAA tweeted. "We're closely monitoring and have provided help to resolve United Airlines flight delays as soon as possible."

This widespread disruption is one of the biggest United Airlines flight delays in history, after other technology failures across the U.S. airline sector.

International Flights Also Affected

United Airlines' international network was not immune. Flights from U.S. hubs like Newark and Chicago to foreign destinations like Delhi, Mumbai, Frankfurt, London, São Paulo, and Panama City experienced cascading delays.

Passengers on flights to and from United's largest hub, George Bush Intercontinental Airport (IAH) in Houston, reported long lines, chaos, and poor communication.

Airline Apologizes for Technical Error

In its X (formerly Twitter) post, United Airlines apologized for the inconvenience and assured customers that safety was still the airline's top priority.

“Our crews are committed to returning to normal operations as soon as possible with safety as our top priority," the airline stated. "We are sorry for the disruption."

The carrier continued that gate space available in destination airports was also a consideration for temporarily suspending departures, and the carrier cautioned passengers to expect additional United Airlines flight delays throughout the evening.

Passengers Express Outrage

As the ground stop dragged into the evening, some passengers complained on social media.

"Stranded on the runway in New Orleans thanks 2 a United system outage. 0 planes in motion. No weight & balance info. Just vibes," wrote one X user.

Another posted: "System-wide outage, all United flights grounded. At the plane. They've given us the option to depart with no ETA."

Other threads also mentioned delays in cities like Detroit, Dallas (DFW), Denver, and Aruba, where travelers were allowed to get off from their planes while waiting.

"We recognize the system failure and are working to repair it so you can proceed on your journey as soon as possible," United Airlines responded on X. "We apologize for this interruption and thank you for your continued patience."

What Comes Next?

As of late Wednesday, United Airlines delays extended throughout the country and the world. Rebound attempts are underway, yet insiders hope it will take a day or two to return everything to normal.

For customers with upcoming travel scheduled, United Airlines suggests keeping an eye on their app or website for real-time information and anticipating schedule changes or rebooking.

This incident adds to growing concerns over the utilization of aged IT systems by the aviation industry and calls for even stronger systems to avoid such major United Airlines flight delays from happening in the future.