Hours after the Federal Aviation Administration ordered a nationwide ground stop Friday that halted flights across the country, including at Midway and O'Hare airports, the agency said departures can resume. Officials blamed “an incredibly old air traffic control system" for instability in air tra ffic control communications during a White House briefing Friday evening. Secretary of Homeland Security Markwayne Mullin said the public was "never in danger" and the flights were grounded due to an "abundance of caution."The Federal Aviation Administration grounded all flights nationwide Friday afternoon at around 2:36 p.m., and an FAA alert said the stoppage was "due to extraordinary circumstances and for reasons of safety."Ground stops were issued at Chicago O’Hare International Airport and Midway International Airport. By 5:30 p.m., O'Hare had reported 328 flight cancellations and 847 delays. Midway saw 30 canceled flights and 186 delays, according to the Chicago Department of Aviation. As of 6:15 p.m. on Friday, 30 flights scheduled to arrive at O'Hare since 2:55 p.m. had been diverted. Ten arrivals scheduled at Midway were also diverted. U.S. Transportation Secretary Sean Duffy said a communication issue affected all of the nation's 22 air traffic control centers that route planes between airports.During the evening briefing, Duffy shifted focus to a political fight, saying the Trump administration had been “asking Congress to fully fund a full build of a brand new air traffic control system.”Secretary of Homeland Security Markwayne Mullin said there was no sign yet that "this was a nefarious attack against us. It's just a telecommunications outage."“Everybody's safe. There's no reason to be concerned about your loved ones if they're flying,” Mullin said.Although the order was lifted, Duffy said he expected it to take a bit to catch up on flight schedules. “Hopefully tomorrow, we are going to start to see far better movement,” he said.Inside O’Hare — the busiest airport in the U.S.— confused passengers wandered around the terminal as luggage piled up on baggage carousels. Long lines of travelers rummaged through hundreds of bags from flights that never took off because of the delay.Video boards displaying flight information were checkered with red and yellow, signifying all the delays and cancellations that forced many travelers to book hotel rooms for the night or rent a car to arrive at their destinations.Prospect Heights residents Matt and Patricia Kowalski arrived at O’Hare two hours early for their annual holiday trip to visit family in Poland, prepared to board a flight to Germany.He learned through the radio on their ride to the airport that a ground stop had occurred, so they decided to wait it out.By 5 p.m., they had already missed their connecting flight and were debating waiting another three hours for the technical issues to pass in the hopes they could keep the trip going.“Maybe we go back home tonight,” Matt said. “There’s no update now.” There is no timeline for restarting flights. Mullin said investigators will look at whether there is any link to the FAA's nationwide rollout of a new artificial intelligence system to help identify problems and reroute planes. But that system operates out of one location near Washington, D.C., and just sends recommendations to the air traffic control centers.The FAA's first alert went out shortly before 3 p.m.The FAA, in a separate statement, said the ground stop was issued "out of an abundance of caution. "Every flight has been accounted for and international flights will be handled on a case-by-case basis," the FAA said.Nashville resident Paul Lindsay was on his way to Mason City, Iowa, with friends before learning of the ground stop at O'Hare."This is nuts," said Lindsay. "It's good to know this is not our problem. Every person in an airport in the United States is running into this problem."The Chicago Department of Aviation said it had no comment and directed questions to the FAA, which did not immediately provide further details.U.S. Rep. Jesús “Chuy” García, D-Ill., a member of the House Transportation and Infrastructure Committee, called for more congressional oversight of the FAA and air traffic control in a statement Friday evening.“My team and I are monitoring the nationwide ground stop that the FAA has ordered, which is causing major travel disruptions and affecting millions nationwide," the statement said. "As a member of the House Transportation and Infrastructure Committee, I will demand answers from the FAA; Congress must be briefed, and there must be a thorough investigation into the cause of this massive disruption to our aviation system.” Jetliners can be seen parked on the runway at O’Hare after the FAA issued a nationwide ground stop Friday.Tyler Pasciak LaRiviere/Sun-Times American Airlines, in a statement, said flights already in the air would continue to their destinations. "We expect disruption to our schedule for the rest of the day, depending on the length of the FAA’s nationwide ground stop," the company said.This is the first nationwide ground stop since January 2023, when a key FAA computer system malfunctioned. Before that, the last time had been after the Sept. 11, 2001 terrorist attacks.The government has been working to overhaul the outdated technology that air traffic controllers rely on since Congress approved $12.5 billion for the project last year, according to the AP. Miles of old copper wires have been replaced with fiber optic lines and old radio systems are gradually being replaced at airports across the country. But much work remains, the AP reported. Duffy has said that another $30 billion will be needed to complete the work, and the White House has begun lobbying Congress to approve it.The FAA recently expanded its use of an AI tool that reroutes flights at O'Hare, though there is no indication that the system is related to the ground stop. The system, called Strategic Management of Airspace Routing Trajectories, or SMART, has been used in Washington, D.C., since September. But the FAA this week said it is now being used at O'Hare to reduce delays. The system has been used to reroute 180 flights across the country, the FAA said. Duffy has said the AI tool would offer recommendations to human air traffic controllers, who would remain in control of rerouting flights.This is a breaking news story. Check back for updates.Contributing: Associated Press ...read more read less