Three unions representing pilots, flight attendants and air traffic controllers are urging President Trump and Congress to end the month-long government shutdown, citing safety and security risks to their members and the public. They warn that some air traffic controllers who are not getting paid could choose to retire, which they say would cripple American air travel.

"In our risk-averse industry, we cannot even calculate the level of risk currently at play, nor predict the point at which the entire system will break. It is unprecedented," the presidents of the National Air Traffic Controllers Association, Air Line Pilots Association and the Association of Flight Attendants said in a joint statement Wednesday.

The unions say some airports are so understaffed that air traffic controllers have to work 60-hour weeks while not getting paid. In addition, the FAA has frozen hiring and training during the shutdown, according to the unions, so there is no help coming.

While many of the current controllers have to keep working, the unions said 20 percent of them are eligible for retirement now, leaving them little reason to work for free.

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