Donald Trump has made his first public comments on the weekend's air travel issues, blaming the Biden administration for leaving "a broken system".
He has also called on Congress for more funding to upgrade America's outdated air traffic control systems.
Thousands more US flights have been cancelled, with Transportation Secretary Sean Duffy warning travel disruptions would continue for another day.
The Trump administration says the air travel havoc triggered by a no-take-off order on Friday could drag on for another day, pushing back its timetable for a return to normal.
Nearly 2,000 more flights were cancelled on Sunday and questions remained over how such chaos could unfold in the world's largest economy, a country that prides itself on its technological prowess.
Stranded passengers wandered through chaotic US airports for a third day.
Officials have blamed Friday's flight chaos on faulty work to upgrade air traffic control communication cables.
On Sunday, President Donald Trump ended uncharacteristic days of silence on the ground stop, but only to blame his predecessor, Joe Biden, for the debacle.
Mr Trump insisted he inherited a mess from the Biden administration and said Congress, which his party controlled for two years, must approve funds to upgrade America's outdated air traffic control system.
"The Biden administration was an FAA disaster,"
