George Bush Intercontinental Airport in Houston has become the symbol for how the ongoing partial government shutdown has wreaked havoc on the nation’s air travel system.

While long security lines have hobbled airports across the U.S., Bush Intercontinental’s problems have been more pronounced. Frustrated travelers at Houston’s largest airport have confronted warnings of four-hour wait times to get through security, as many Transportation Security Administration workers aren’t showing up for their shifts since they’re not getting paid during the shutdown.

“And we’ve been in this airport since 8 o’clock in the morning. Very tired, queuing and queuing and very slow,” Edgaer Fernando, who was traveling to Guatemala, said on Tuesday.

Union and airport officials have offered a variety of reasons why Bush Intercontinental seems to be worse than other airports.

These include the Houston airport having one of the highest callout rates of TSA workers in the country due to the economic challenges they are facing, higher passenger traffic as the airport is a major hub for United Airlines, and a busy tourism month for Houston.