ATLANTA — Problems with the communications system used by air traffic controllers grounded departing flights across the country starting Friday afternoon, including at Georgia’s Hartsfield-Jackson Atlanta International Airport.

“FAA Ground Stop Alert,” read a red banner atop the Hartsfield-Jackson website. The message said the Federal Aviation Administration suspended departures from Atlanta and other major airports.

The airport urged travelers to check with their airlines for updates, promising to provide information as it becomes available.

U.S. Transportation Secretary Sean Duffy posted on X at 4:16 p.m. Eastern time blaming the stoppage on a “communication issue” affecting all air route traffic control centers. His post said that FAA technicians were investigating.

About 45 minutes later, the FAA posted on X that the agency had, “out of an abundance of caution,” grounded flights due to a “temporary telecommunications outage.”

“Every flight has been accounted for and international flights will be handled on a case by case basis,” the post added.

By 7:30 p.m., there were about 10,000 delays within, into or out of the United States on Friday, according to FlightAware, a flight-tracking website. The site counted more than 4,000 cancellations.

Around the same time, the site reported 151 delays and 95 cancellations at Hartsfield-Jackson between 5 p.m. and 9 p.m. It reported more than 2,100 delays and nearly 1,200 cancellations nationally for the same four-hour span.