Elected officials and union leaders warned on Thursday of growing risks to the nation’s aviation system as the partial government shutdown threatened to stretch into a second month and workers face the prospect of another pay period without a check.

“The truth is that Americans who are flying today are less safe than what our standards have been,” Sen. Mark Warner, D-Va., said as he stood with a group that included air traffic controllers, flight attendants and aviation safety specialists at Reagan National Airport.

Union leaders said the nation’s aviation system works because it is multilayered, and while many workers remain on the job, others who perform critical functions have been furloughed and their absence leaves the system – and those who use it – vulnerable.

“Are we less safe today? We are less safe,” said Sara Nelson, international president of the Association of Flight Attendants.

“The critical networks of layers of safety and security are not in place because we have people furloughed who fill those roles,” Nelson said. “As flight attendants, we know what happens when there is a gap in security.”

An estimated 800,000 federal employees are furloughed or working without pay during the shutdown. Agents with the Transportation Security Administration and air traffic controllers and others with the Federal Aviation Administration are among those working without pay.