Travelers flying this week may want to arrive at the airport earlier than usual as the Department of Homeland Security shutdown stretches into its fourth week.

Lines at several airports across the country have stretched through concourses, with some travelers waiting more than an hour to pass through security.

About 300 Transportation Security Administration agents have quit their jobs since the shutdown began, according to Transportation Secretary Sean Duffy, who said employee callouts have also doubled during the standoff. TSA agents have already missed a partial paycheck and are now missing a full pay period.

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Some airports, including those in Denver and Seattle, have begun asking for donations to support TSA workers during the shutdown, which Duffy blamed on political gridlock.

The funding dispute centers on immigration enforcement policy.

Democratic lawmakers have proposed changes to immigration enforcement as part of negotiations to restore DHS funding. The proposals include banning face masks worn by federal immigration agents, requiring judicial warrants before agents can enter private property, mandating body cameras for all agents, and establishing a standard uniform with a badge, identification number and last name prominently displayed.

Republicans have not agreed to all of the proposals, leaving DHS funding unresolved.

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