Some US airports may have to shut as travellers reportedly endure long wait times at security following a shutdown that's seen 50,000 staff go unpaid.
The claim came from the acting head of the Transportation Security Administration (TSA), who told a committee it was a "dire situation" that should never be allowed to happen again.
Ha Nguyen McNeill said nearly 500 TSA employees - who screen passengers and luggage - had quit so far after not receiving pay since mid-February.
She said multiple major airports were seeing 40% to 50% call-out rates (a measure of absence), compared with an average of 4% normally, because staff "simply cannot afford to report to work".
She added: "Multiple airports are experiencing days where 40-50% of their staff are calling off because they simply cannot afford to report to work.
"This has lead to the highest wait times in TSA history, with some wait times greater than 4.5 hours."
A resolution does not appear imminent as Democrats and Republicans still cannot agree a deal on funding the Department of Homeland Security, the body that encompasses the TSA.
Democrats want changes to immigration and deportation operations after the controversial killings of two people in Minneapolis earlier this year by Immigration and Customs Enforcement (ICE) officers.
ICE agents have been sent to some airports by the Trump administration for what Ms McNeill called "non-specialised screening functions", but opponents say the move is inflammatory.
White House spokesperson Karoline Leavitt said they were helping reduce wait times - though "not as much as we like".
In the meantime, many TSA workers are being pushed to the brink, and are resorting to desperate measures.
"Some [staff] are sleeping in their cars, selling their blood and plasma, and taking on second jobs to make ends meet, all while being expected to perform at the highest level when in uniform to protect the traveling public," Ms McNeill told the House homeland security committee.
She said assaults had also increased by 500% increase since the shutdown began in mid-February, as some passengers take out their frustrations on staff.
The boss of Houston airport warned security waits of up to four hours - that have seen queues wind down multiple floors - could get longer if a deal isn't done soon.
In a video on the airport's website, Jim Szczesniak said employees working in areas such as IT, finance and maintenance had been redeployed to try to manage the lines. However, he warned it wasn't sustainable.
New York LaGuardia was another airport seeing long lines on Wednesday afternoon, with people queuing virtually the entire length of Terminal B.
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The TSA boss also agreed during her committee appearance that there could be problems when fans arrive for the World Cup in June.
Ms McNeill said it took four to six months to train new staff, and added that job applications had dried up significantly, raising questions about replacing those who have quit.
Meanwhile, the White House has rejected Elon Musk's offer to pay TSA wages during the shutdown, according to CBS News.
The world's richest person made the offer on X at the weekend.
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