Operations are returning to normal after a runway equipment issues prompted ground stops at Newark Liberty and Hartsfield-Jackson Atlanta International airports Sunday, the Federal Aviation Administration announced.

More than 450 flights were delayed Monday causing chaos at Newark and Atlanta international airports following the weekend’s ground stop order over air traffic control failures. The Federal Aviation Administration (FAA) issued a warning that a second ground stop order was possible given the situation at Hartsfield-Jackson Atlanta International — the busiest airport in the US — which has seen more than 370 delays as of Monday afternoon,

Transportation Secretary Sean Duffy said the number of flight cutbacks would fluctuate by time of day, with most targeting afternoon hours when international arrivals make the airport busier.