United Airlines has announced that all flights, nationwide, will be delayed from departure due to what the airline is citing as a “technology issue.”

An undisclosed “technology issue” has grounded United Airlines flights across the U.S. United Airlines said in a statement Wednesday that flights on major routes were being held at their departure airports because of a technology issue.

Around 35% of the carrier’s scheduled flights faced delays on Wednesday night, while 4% were cancelled as the airline faced the residual impact of a technical snag.