Boston has so far managed to avoid long lines during the partial government shutdown. But that's likely to change as more security agents walk off the job.

More than 300 TSA officers have quit since the partial government shutdown began last month, according to agency statistics obtained by CBS News.

The U.S. transportation secretary also said the number of TSA agent “callouts” have doubled from what they were before the shutdown.

Union representatives say the shutdown is straining TSA workers, some of who are still digging out of debt from last year's shutdown.

The ongoing Homeland Security shutdown causes widespread airport chaos and hardship for federal workers. Unpaid TSA agents and severe weather lead to major travel delays and cancellations.

The partial shutdown began in mid-February after Congress failed to pass funding for the Department of Homeland Security, which oversees TSA. Roughly 50,000 TSA officers are continuing to work but without regular pay during the funding lapse, raising concerns about staffing shortages and absenteeism as spring break travel ramps up.