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The government shutdown continues to put extraordinary pressure on the nation’s air-travel system, with as many as one of every 10 transportation security officers failing to show up for work and reserve workers having to be flown in to bolster depleted ranks at some airports.

The rate of unscheduled absences of airport screening agents dropped to 7.5 percent on Monday, down from 10 percent the day before, the Transportation Security Administration said. But the agency still had to deploy some backup officers to big airports, including Newark Liberty International in New Jersey, a spokesman for the agency said on Tuesday.

The agency’s force of more than 50,000 officers learned on Tuesday that they, like the rest of the 800,000 federal workers who have not been paid during the monthlong shutdown, would miss another paycheck this week. The agency said that many of the absentees had cited financial troubles as their reason for not coming to work, a signal that the call-out rate is likely to continue rising until the shutdown ends. The absentee rate for Tuesday will be available on Wednesday.

Transportation experts and elected officials have begun asking how much longer the air-travel system can continue running safely.