The Trump administration is being sued by the National Air Traffic Controllers Association for forcing employees to work without pay, NBC News reports.

The big picture: On Thursday, air traffic controllers received their first paycheck showing $0.00 as a result of the government shutdown. The administration is also being sued by the National Treasury Employees Union and the American Federation of Government Employees, with other organizations likely to follow as the shutdown officially ties the record for longest in U.S. history.

Go deeper: Shutdown, Day 21 — "Payday without pay"