Delta Warns Flyers That Resetting Its Network After National Ground Stop Will Take Time

Delta Air Lines isn't pretending the recovery will be instant. After the Federal Aviation Administration lifted Friday's nationwide ground stop, the carrier said it will take time to reset its operations, and it's steering travelers toward its app for updates and notices as the picture evolves.

For passengers, Delta laid out its playbook: flight changes and free rebooking for anyone whose trip gets fully canceled. The airline said it will keep travelers posted as the reset moves along.

The disruption left a deep mark nationally. Flight Radar 24 counted more than 5,000 canceled flights and said the number was still rising rapidly. Chicago O'Hare International Airport took the hardest hit with 459 cancellations, followed by Hartsfield-Jackson Atlanta International Airport and New York's LaGuardia Airport.

The cause is still under the microscope. DHS Secretary Markwayne Mullin and the FAA pinned the ground stop on a telecommunications issue, and Mullin said there is no indication of a nefarious attack or foreign interference, though he stressed nothing is ruled out and agencies are still looking into it.

Not everyone has a clean answer yet. CNN reported, citing a person familiar with the matter, that the FAA doesn't know what is going on, while another source said the outage knocked out air traffic control radars and radio frequencies, leaving controllers in the dark on the root cause. Mullin addressed the situation at the White House alongside Transportation Secretary Sean Duffy.