(CNN) The partial government shutdown is three weeks old, and it's gone on long enough for some of the 800,000 federal employees impacted to start missing pay.

This weekend is the first time that many of them are receiving paychecks with no money.

Take, for instance, William Striffler, an air traffic controller at Newark Liberty International Airport in New Jersey.

He gave CNN permission to use this image of his pay stub. During this particular pay period, Striffler worked 64 hours. The amount listed under "net pay?" $0.00.

Working long hours without getting paid is a tough thing to deal with, Striffler said.

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