If there's anything that can bring Americans together to demand government action, it's long lines at airport security.

Those lines continued to grow on Sunday and remained in some places on Monday as a partial government shutdown left the Department of Homeland Security and its Transportation Security Administration unfunded and their agents unpaid at the height of the spring break travel season.

Airports are now telling passengers to arrive up to three hours early to clear security in time for their flights.

The TSA on Sunday called on Congress to resolve the impasse over the immigration enforcement policies that have left the DHS unfunded for a month. The agency said hundreds of unpaid agents have quit.

"3+ hour TSA lines for travelers. 300+ TSA officers who have quit. A $0 paycheck for those continuing to serve. Enough is enough," the agency said in an X post on Saturday.

A group of airline CEOs also sent a letter to Congress on Saturday calling on Republicans and Democrats to figure it out. "Americans —who live in your districts and home states — are tired of long lines at airports, travel delays, and flight cancellations caused by shutdown after shutdown," the letter, which was signed by the CEOs of Delta, United, American, JetBlue, and others, says.

By Monday, lengthy lines were still present at several airports, though they had calmed at some locations that had seen long lines over the weekend.

Just before 7 a.m. local time on Monday, lines at Terminal C in Newark Airport were over 40 minutes, while lines at two of JFK's terminals exceeded 30 minutes.

At Dallas-Fort Worth, lines at many security checkpoints exceeded 20 minutes.

Austin-Bergstrom International was one of the worst-affected airports over the weekend, due in part to an influx of travelers for the SXSW festival.

Photos and videos shared by travelers over the weekend showed lines stretching from the terminal building into the parking lot. Those lines persisted early on Monday morning, but by just before 6 a.m. local time, lines had abated, according to the airport's X account.

While lines had modulated somewhat, many airports were still telling passengers to leave more time than usual to clear security on Monday. Dallas-Fort Worth Airport told travellers to allow at least 2 hours for domestic flights, while Austin advised leaving 2.5 to 3 hours.

In Atlanta, many flights were facing lengthy delays or cancellations due to a thunderstorm on Monday. Fox 5 Atlanta also reported that security wait times were over an hour and a half around 6 a.m. local time.

How to check wait times

The easiest way to avoid the stress of missing your flight is to arrive as early as you can. Many airports are advising travelers this week to arrive up to three hours before their flight.

To check TSA wait times, many airports, including major hubs like Atlanta, Houston, JFK, Newark, Philadelphia, Dallas-Fort Worth, and Denver, post them live on their websites.

These can also provide more specific insights. For example, DFW's website shows the wait times at each checkpoint.

While broadly reliable, some airport websites aren't always accurate. On Monday morning, Atlanta airport's website appeared to be experiencing a glitch, as it displayed 0-minute wait times for all TSA checkpoints when Business Insider checked, despite reports of lengthy lines.

You can also use the MyTSA mobile app. It provides estimated wait times in 15-minute intervals based on average checkpoint data. The app, however, will use historical data if the live data cannot be retrieved. The TSA also says it is not "actively" managing its sites during the partial shutdown, and so the app may not always be updated.