Potentially hundreds of thousands of Americans could have their jobs impacted as the deadline looms for Congress to pass spending bills to avoid a total government shutdown.

Funding expires on Sept. 30, and House Republicans are still divided on spending negotiations, with members of the House Freedom Caucus openly leveraging a potential shutdown to meet their demands.

If that were to happen, all “non-essential” federal agencies would close and their employees would be furloughed. Additionally, air travel and food inspections could be delayed, and even national parks could soon pause operations.

If a shutdown does happen, here are jobs that would be affected:

What to know:If a government shutdown occurs, how would it affect you?

The US Capitol is seen during a government shutdown in Washington, DC, December 27, 2018. (Photo by ANDREW CABALLERO-REYNOLDS / AFP) (Credit: ANDREW CABALLERO-REYNOLDS, AFP/Getty Images)

Federal employees

If the government shuts down, hundreds of thousands of federal employees will find themselves either working with pay, working without pay or furloughed with no income.

Federal employees deemed essential, such as law enforcement and those involved in national defense, would continue working through a shutdown. However, many federal workers who are approved to work during the shutdown may have to do so without pay, according to the U.S. Office of Personnel Management (OPM).

Others will be sent home and won't be working at all, including congressional staffers. The good news is that furloughed employees who are not allowed to work or who do not receive paychecks are still guaranteed back pay due to legislation passed in January 2019. Furloughed employees can also apply for unemployment benefits, OPM says.

State employees relying on federal funds

State employees whose employers depend on federal funds to operate could be out of work during a shutdown if their work is deemed by the government to be non-necessary. State employees who receive salaries from private employers who do not rely on federal funds wouldn’t necessarily be impacted, though certain state employees could be furloughed until a shutdown passes.

Military and federal law enforcement personnel

Service members will not be paid although they will be required to continue to report for duty.

“Military personnel will not be paid until such time as Congress appropriates funds available to compensate them for this period of service,” the Defense Department said in a September memo to Pentagon leaders preparing for a potential lapse in spending.

More:Will military get paid in a government shutdown?

The government has about 1.3 million active-duty service members and 800,000 reservists.

The Pentagon is also likely to pause military recruitment and operational planning. The pause in pay and furloughs will have impacts that go beyond the US' borders.

TSA and air traffic controllers continue work while trainees pause

Air traffic controllers are considered essential workers even during a government shutdown, so they’ll continue working, even though they won’t be getting paid.

However, 1,000 air traffic controllers undergoing training by the Federal Aviation Administration would be furloughed if the increasingly likely government shutdown begins this weekend.

That's according to Transportation Secretary Pete Buttigieg, who said in a news conference Wednesday that a shutdown even for a few days would prevent the FAA from hitting staffing targets for the upcoming year.

Controllers already trained and on the job would continue working through a shutdown, without pay until its conclusion, but training for new hire would cease. The timing of the looming shutdown could not be more dire, Buttigieg said, especially amid an already existing air traffic controller shortage.

The White House on Wednesday said a government shutdown would mean more than 13,000 air traffic controllers, 50,000 transportation security officers, and thousands of other FAA and TSA personnel showing up to work without immediate pay.

National parks prepare for furloughs

Thousands of national park rangers would be furloughed in a government shutdown, the Department of Interior said in a Friday news release.

Most national parks would be entirely closed to the public in the event of a shutdown.

Wayne Freimund, a professor of recreation resource management at Utah State University-Moab, told USA TODAY the National Park Service typically goes through a process to determine its most essential employees, like those who protect park resources or provide safety assistance.

But the staffers that park visitors often interact with should expect to be furloughed, he said.

Dig deeper:Can I visit a national park during a government shutdown? Here's what to know

Furloughs at FDA, NIH, USDA

Furloughs at the the National Institutes of Health (NIH) and the Food and Drug Administration (FDA) could lead to delays in new clinical trials for medical treatments, and food safety inspections. Additionally, many inspections of hazardous waste sites, drinking water, and chemical facilities could be stopped.

An estimated 50,000 workers at the United States Department of Agriculture would be furloughed in the event of a shutdown, Agriculture Secretary Tom Vilsack said Monday at a White House press briefing.

More:Why Gaetz and small group of GOP lawmakers have power to cause a government shutdown

Subcontracted government workers could lose wages altogether

Subcontracted workers who are employed by a third party may never see the wages they lose from not being able to work during a government shutdown.

Those who work for a government vendor most likely won't get any backpay, Marlene Patrick Cooper president of UNITE HERE Local 23 President, which represents more than 600 of these subcontractors, told USA TODAY. Additionally, hourly employees could lose all of their income for the duration of a shutdown, and possibly risk losing health coverage and retirement contributions during that period.

“When you're living paycheck to paycheck, and then you don't get any money to come in, that's a real struggle. That's a hurtful thing,” Willie Price, 63, whose worked in various roles at the Library of Congress for 40 years told USA TODAY.

U.S. Postal Service not affected by a possible government shutdown

The Postal Service is an independent entity generally funded by the sale of its products and services − not tax dollars − and it will not be impacted by a government shutdown, USPS said in a statement. Because it's not impacted, employees will be paid normally.

"Postal Service operations will not be interrupted in the event of a government shutdown, and all Post Offices will remain open for business as usual," the statement said.

Contributing: Savannah Kuchar, Sudiksha Kochi, Candy Woodall, Bart Jansen, USA TODAY staff

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