BREAKING: A ground stop was issued Wednesday evening for many United Airlines flights across the U.S., the FAA said.

“Due to a technology issue, we are holding United mainline flights at their departure airports,” the airline said in a statement to ABC News. “We expect additional flight delays this evening as we work through this issue. Safety is our top priority, and we’ll work with our customers to get them to their destinations.”

The impacted airports include Newark, San Francisco, Chicago, Denver, and Houston.