Travelers across the United States are encountering unusually long airport lines, with some of the most severe delays reported in Houston, where security wait times have surpassed four hours during a partial government shutdown.

Ongoing staffing shortages at the Transportation Security Administration are driving the disruptions, as hundreds of agents have missed paychecks and are calling out of work, leaving airports struggling to maintain passenger screening operations.

At George Bush Intercontinental Airport in Houston, nearly 40% of TSA personnel failed to report for duty — the highest absentee rate nationwide, according to US media reports.

Authorities warn the situation could deteriorate further without action from lawmakers. Officials fear that conditions "will only get worse at airports across the US until Congress ends this shutdown".

Houston’s airport is currently running only about one-third to half of its TSA checkpoints, according to Jim Szczesniak, director of aviation for the Houston Airport System.

"That's 100% spring break loads going through the airport, being processed through less than 50% of our TSA lanes," he noted referring to the spring break travel season. "That is not sustainable."

Passenger volumes are expected to climb even higher with several major events scheduled in Houston this weekend, potentially worsening congestion. The Astros’ season opener, a golf tournament, and two NCAA Tournament Sweet 16 games are all set to draw additional travelers.

In response, the TSA plans to send at least two dozen officers from its National Deployment Office to Bush airport on Thursday, according to the Houston mayor’s office, which spoke to CBS News.

Earlier in the week, the Trump administration announced that hundreds of US Immigration and Customs Enforcement agents had been dispatched to 14 airports, including those in New York, Atlanta and Houston, to help ease staffing shortages.

US President Donald Trump praised the effort on Wednesday, saying the agents are doing "an unbelievable job" at airports. He added that the National Guard could also be deployed "if we need to" to support TSA and ICE operations. He blamed Democrats for the staffing crisis, saying they "don't want to pay" the agents.

Democratic lawmakers, however, have declined to approve funding for the Department of Homeland Security without new restrictions on immigration enforcement, following public outrage over the fatal shooting of two US citizens in Minneapolis.

Republicans have pushed back against Democratic proposals tied to TSA funding as negotiations over ICE reforms continue.

There is little indication that the impasse over funding will be resolved soon.

Meanwhile, billionaire Elon Musk reportedly offered to cover TSA workers’ pay during the shutdown, but the White House declined the proposal on Wednesday, according to multiple sources cited by CBS News.

A senior TSA official said Wednesday that more than 450 agents have resigned since the shutdown began.

Although that figure represents a small portion of the roughly 50,000 TSA workforce, the departures — combined with widespread absences — are contributing to longer wait times nationwide.

Testifying before a congressional oversight committee, TSA Acting Administrator Ha Nguyen McNeill warned that the staffing losses could have "dire" consequences as the US prepares to co-host the FIFA World Cup this summer.

"At this point if we bring on any new [TSA agents], those folks will not be deployed in time by FIFA," she said.

McNeill added that the agency is closely tracking attrition rates and may need to adjust staffing plans if conditions worsen.

"If we see any spikes, we'll have to pivot and assess how we are going to staff the FIFA locations adequately."