New York, New York - The Trump administration said Sunday the air travel havoc triggered by a no-takeoff order could drag on for another day, pushing back its timetable for a return to normal.

Hundreds more flights were canceled, and questions remained over how such chaos could unfold in the world's largest economy, a country that prides itself on its technological prowess.

Officials blame Friday's huge snafu on faulty work to upgrade air traffic control communication cables.

President Donald Trump on Sunday ended uncharacteristic days of silence on the ground stop, but only to blame his predecessor Joe Biden for the debacle.

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Trump insisted he inherited a mess from the Biden administration and said Congress, which his party has controlled for two years, must approve funds to upgrade America's outdated air traffic control system.

FAA chief Bryan Bedford had said Saturday that air travel for millions of Americans stranded at airports would return to normal by the close of business on Sunday.

But Transportation Secretary Sean Duffy said Sunday morning it will actually take longer to get planes, crews and travelers to where they need to be.

"So, in the airspace, we're going to see things come back to normal today, but probably fully normal tomorrow," Duffy said on ABC News.

"We had airplanes and crews out of position because of Friday, so it takes a little bit of time to do that."

Duffy also flatly rejected calls for his resignation over the travel chaos, insisting he inherited woefully outdated air traffic control infrastructure, such as, he said, radar equipment that dates back to the 1960s.

"So when we do work, and things go wrong, of course I'm the secretary. But I also have to acknowledge what was delivered to me," Duffy said in an interview on CNN.

As of Sunday morning, 1,460 flights within, into or out of the US had been canceled, according to the travel monitor site flightaware.com.

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The Trump administration has blamed Friday's ground stop – meaning no planes can take off – on a botched replacement of old copper wire communication lines.

Friday's disruption was only the second time such a ground stop had been issued in US airspace, which is among the busiest in the world, since the 9/11 attacks.

The ground stop not only plunged US air travel into chaos, it also raised serious concerns about the country's aging infrastructure.

Duffy has appealed for $50 billion in funds to upgrade and modernize the air traffic control system, and called for Congress, which controls the purse strings of the US government, to "meet this moment."

But Democrats quickly pounced to say Congress under Trump's Republicans could already have done this.