FILE – A Southwest Airlines jet arrives at Sky Harbor International Airport, Dec. 28, 2022, in Phoenix. With its flights now running on a roughly normal schedule, Southwest Airlines is turning its attention to luring back customers and repairing damage to a reputation for service after canceling 15,000 flights around Christmas. The disruptions started with a winter storm and snowballed when Southwest’s ancient crew-scheduling technology failed. (AP Photo/Matt York, File)

NEW YORK (AP) — The world’s largest aircraft fleet was grounded for hours by a cascading outage in a government system that delayed or canceled thousands of flights across the U.S. The White House initially said that there was no evidence of a cyberattack behind the outage that ruined travel plans for millions of passengers. President Joe Biden said Wednesday morning that he’s directed the Department of Transportation to investigate. A order to ground all departing flights by the Federal Aviation Administration was lifted, but there are already 1,000 flight cancelations and more than 7,000 delayed flights. That number is expected to grow as the air travel network comes back to life.