Without paychecks, some federal employees have resorted to picking up temporary jobs to make ends meet.

The TSA said it is "optimizing resources" to ensure screening lanes are properly staffed but warned that airports may exercise contingency plans because of call-outs and traveler volume.

TSA employees screened 1.78 million passengers Sunday. Of those, "99.9 percent" waited less than 30 minutes, the agency said, and 93.1 percent waited less than 15 minutes. Saturday, the sickout rate was 8 percent.

Baltimore-Washington International Thurgood Marshall Airport said it closed a checkpoint Sunday to "efficiently use staffing." The airport tweeted that such closures were common before the shutdown and have "minimal, if any, impact on passengers."