The unions that represent the nation’s air traffic controllers, pilots and flight attendants issued a dire warning on Wednesday, calling the government shutdown an “unprecedented” and “unconscionable” safety threat that is growing by the day and must end.

In a joint statement, the heads of the unions, which represent more than 130,000 aviation professionals, said that on Day 33 of the shutdown, major airports were already seeing security checkpoints close, and more closings could follow; safety inspectors were not back on the job at pre-shutdown levels; and analysts’ ability to process safety reporting data and take critical corrective action had been weakened.

“We have a growing concern for the safety and security of our members, our airlines and the traveling public due to the government shutdown,” the joint statement said. “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.”

[Here is our guide to the government shutdown and updates on where things stand.]

The admonition came as the partial shutdown continued to put extraordinary pressure on the nation’s air-travel system. Already, as many as one of every 10 transportation security officers is not showing up for work and reserve workers are being flown in to bolster depleted ranks at some airports — a point the union presidents raised in their statement.