United Airlines flights on major routes were grounded Wednesday because of a technology issue, and additional flight delays were expected into the evening, the airline said.

An alert on the Federal Aviation Administration website said all United flights destined for Chicago were halted at their departing airports. The agency said Denver, Newark, Houston and San Francisco airports were also impacted by halted flights.

"Safety is our top priority, and we'll work with our customers to get them to their destinations," an emailed statement from the Chicago based-airline said without disclosing the specifics of the problem.

An AP journalist had boarded a United plane at the Louis Armstrong New Orleans International Airport for a trip to Houston when flight attendants announced a "systemwide" problem had grounded flights. They then sent passengers back to the terminal.

Another traveler, Johan Kotze, was at the New Orleans airport to begin a journey to the Indian Ocean island nation of Mauritius for vacation. Getting caught up in flight delays for him likely meant he would miss connecting flights along the way and would have to rebook not only the flights but a car and accommodations as well.

"It's not very nice," he said of the experience.

United Airlines apologized on social media to upset customers who were facing delays and hours sitting in planes on runways.

"Hey there, we apologize for the travel disruption today," the airline told a customer on the social platform X. "Our teams are working to resolve the outage as quickly as possible. Thank you for your patience."