By Chris Isidore, CNN

(CNN) — America hasn’t had enough air traffic controllers for more than a decade – and the recent government shutdown might have made it even worse.

The stress of not being paid for those 44 days, on top of already harsh working conditions, spurred many to leave the workforce, according to Nick Daniels, president of the National Air Traffic Controllers Association, the union representing controllers.

Transportation Secretary Sean Duffy said it also prompted many to retire early.

Replacing them could take years – and the shutdown underscored the stakes when the country lacks controllers: canceled flights, delays and an even more miserable travel experience overall.

Daniels wouldn’t estimate the number of controllers lost, referring CNN to the FAA. The FAA did not

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