The George Bush Intercontinental Airport in Houston was forced to close one of its security screening checkpoints on Sunday because of the partial government shutdown, which has caused a shortage of workers.

The airport sent out a message on Twitter saying the Transportation and Security Administration checkpoint for Terminal B would be closed and passengers would be rerouted to other terminals.

TSA agents have been among the federal employees forced to work without pay during the government shutdown, which became the longest in American history this weekend. Many of the TSA’s workers have called in sick rather than go to work, although the agency said the effectiveness of its security screenings would not be compromised during the shutdown.

Around 800,000 federal workers missed their first paychecks on Friday, although Congress passed a bill last week to grant back pay to those workers and the president has signaled that he will sign it.

Sylvester Turner, the mayor of Houston, linked the closure on Sunday directly to the shutdown and urged travelers to venture to the airport at least two hours early to make it through screenings.

“Shortage of TSA workers, unpaid during the US gov’t shutdown, is causing this change,” Turner wrote on Twitter. He said the B terminal was solely used by United Airlines flights.

Advice to always get to @iah 2 hours before your flight is especially important today. Shortage of TSA workers, unpaid during the US gov’t shutdown, is causing this change. Terminal B is solely @united flights. pic.twitter.com/ijCKa4k1NP — Sylvester Turner (@SylvesterTurner) January 13, 2019

Last week, the TSA Council president for the American Federation of Government Employees said that agency workers had been suffering extreme financial hardship during the shutdown and that some employees had already walked off the job.

“Every day I’m getting calls from my members about their extreme financial hardships and need for a paycheck,” Hydrick Thomas said in a statement. “Some of them have already quit and many are considering quitting the federal workforce because of this shutdown. The loss of officers, while we’re already shorthanded, will create a massive security risk for American travelers since we don’t have enough trainees in the pipeline or the ability to process new hires.”

The ongoing shutdown has stretched into its fourth week with no end in sight as President Donald Trump has remained steadfast in his demands for some $5.7 billion for a wall along the southern border. He has walked back from plans to declare a national emergency to do so without congressional approval, but Republicans and Democrats remain at an impasse as to how they can resolve the conflict.

Miami International Airport made a similar move on Saturday, saying one of its checkpoints at a smaller terminal would close early each day.