Transportation Secretary Sean Duffy said Tuesday that the department will run out of money for air traffic control student stipends in about a week because of the partial government shutdown, threatening a pipeline for a workforce already strained by personnel shortages.

Duffy said at a news conference at LaGuardia Airport in New York City that “several” air traffic control students are dropping out of the academy because of the threat of losing the stipend, which he described as a “small amount of money” that helps students make ends meet while attending school.

“This shutdown is making it more difficult for me to accomplish those [hiring] goals,” he said. “We tried to plan for this. We tried to preserve as much money as possible. … When we have new controllers that are being trained up, they don’t make a lot of money, and that’s the base pay they get, and they’re having a hard time making ends meet on the pay itself.”

The nation’s air traffic control system has long faced personnel shortages. Duffy estimated Tuesday that the system is about 2,000 to 3,000 controllers short despite a February plan that he said would “supercharge” hiring by creating an academy graduation bonus and raising the starting pay for new controllers by 30 percent.

The program provides a $10,000 award for academy graduates who are assigned to one of 13 hard-to-staff air traffic facilities and $5,000 bonuses for graduates and new hires who successfully complete the initial qualification training. Duffy said in May that the Federal Aviation Administration was set to hire 2,000 new controllers through the next year.

Lawmakers remain at an impasse in negotiations to reopen the government as the shutdown continues into its fourth week. Air traffic controllers missed their first full paycheck Tuesday because of the shutdown. Air Traffic Control Academy instructors are also not being paid.

Duffy said at the news conference that flight delays due to controller staffing shortages jumped from about 5 percent before the shutdown to about 44 percent on Sunday. The delays were at 24 percent Monday, he said, as they hit major airports like Los Angeles International over the weekend.

Duffy added that the FAA budget doesn’t offer “a lot of leeway” to fund controllers. He urged the Senate to pass a bill from Sen. Ted Cruz, R-Texas, that would pay for FAA personnel “whose services are required for the safe and orderly operation of the national airspace system,” including air traffic controllers.