Hundreds of Transportation Security Administration officers, who are required to work without paychecks through the partial government shutdown, have called out from work this week from at least four major airports, according to two senior agency officials and three TSA employee union officials.

The mass call outs could inevitably mean air travel is less secure, especially as the shutdown enters its second week with no clear end to the political stalemate in sight.

“This will definitely affect the flying public who we (are) sworn to protect,” Hydrick Thomas, president of the national TSA employee union, told CNN.