The Republican president had been notably silent on the ground stop since it began Friday afternoon, posting on social media about unrelated topics while frustrated passengers were stranded at airports and his administration worked with airlines to restore normal travel.

In a new post on his social media platform, Trump said his administration has begun upgrading the system but argued the work should not proceed in "drips and drabs." He wrote that if Congress approves the funding, "we can get it built quickly and efficiently," adding that "much of our current air control system is 50 years old - RIDICULOUS!"

Congress approved $12.5 billion for the Federal Aviation Administration last year as part of a sweeping tax cut package, but Transportation Secretary Sean Duffy has repeatedly described that money as a down payment on a broader overhaul. In a separate post, Trump criticized former President Joe Biden's administration for what he said was making an "old and broken system worse than when they began." Biden signed a major infrastructure law in his first year that set aside $25 billion for the FAA to improve airports and air traffic control towers, redevelop terminals and upgrade the foundation of the air traffic control system.

Duffy served as the administration's public face on the ground stop during the Sunday news shows, pressing Congress for billions of dollars in upgrades. "I can't apologize for what was passed on to us. And I can't blame Republicans or Democrats, because it's all of them. It goes back, 20, 25, 30 years of a lack of investment," he told NBC's "Meet the Press."

In a post on X, Duffy said contractor L3Harris Technologies had secured two routers from FAA facilities in Texas and Arkansas and was conducting "deep diagnostics" on the equipment. He has said the problem began when L3Harris was replacing a section of old copper wire with new fiber wire, causing the system to overload. After the wire was replaced at the site in El Dorado, Arkansas, and the router was turned on, a problem cropped up at a facility in Amarillo, Texas, cascading into the ground stop. "We didn't think that should or would happen," Duffy told ABC's "This Week."

As for the traveling public, Duffy told CBS' "Face the Nation" that "we have some delays in the airspace right now," but that by the end of the day and into Monday, "we should be running at full capacity." In a ground stop, airplanes and crews are taken out of position, he said, "so it takes a little bit of time for the airliners to get back ... at full capacity and operation but we're well on our way."

The episode has thrust the long-deferred question of air traffic control modernization into the center of a funding fight, with the administration pointing to decades of neglect and pressing lawmakers to act on a system that travelers depend on every day.