(CNN) A partial government shutdown wouldn't cancel Christmas, but some of the people making things run smoothly ahead of and after the holiday could be affected.

About a quarter of the federal government is set to close late Friday when funding for nine Cabinet departments and smaller agencies expires. That means about 380,000 employees will be placed on furlough and another 420,000 will be expected to work without pay.

Holiday travel will go on

Planning to take a plane or train to your holiday destination?

The Transportation Security Administration will be on the job to screen passengers, and Federal Aviation Administration air traffic controllers will be directing planes.

Amtrak, a federally owned corporation rather than a government agency, will be open. Federal Railroad Administration inspectors will also continue to work. According to the railroad administration's shutdown plans: "Data shows that when Inspectors are not visible, less compliance is more likely to occur, which may lead to higher accident/incident rate."

US Customs and Border Protection checkpoints will remain open for international travelers.

TSA Administrator David Pekoske pointed out that federal employees who are required to work during a shutdown will eventually be paid, but not until the government reopens.

"But we're certainly hoping that there is no shutdown," he told reporters this week.

Have international travel in your future? The State Department will continue processing passports.

Christmas gifts will arrive on time

If you shipped them on time, that is.

The Postal Service does not receive federal funds for its operations and will not be affected by a government shutdown. It expects to deliver nearly 16 billion pieces of mail and packages this season. Post offices will close at noon on Christmas Eve as planned.

Law enforcement and safety continue

Federal employees who keep people safe or protect property must typically report to work during a shutdown.

That means many law enforcement officers will keep their schedules.

It also means the National Aeronautics and Space Administration will keep mission controllers on hand to support astronauts on the International Space Station but will close NASA facilities to visitors and suspend some research projects.

Safety inspectors -- such as the Interior Department's Bureau of Land Management and the Transportation Department's Pipeline and Hazardous Materials Safety Administration officials, who monitor oil pipelines like the Trans-Alaska Pipeline -- will continue their work.

It's a similar story at the Agriculture Department's Food Safety Inspection Services, which inspects meat and poultry, and the Consumer Product Safety Commission, which will keep a bare-bones team to consider potential recalls of products that "create a substantial and immediate threat to the safety of human life."

Forecasters at the National Weather Service, which is part of the Commerce Department, and earthquake monitors at the US Geological Survey, part of the Department of the Interior, will stay on the job, too.

Although the Justice Department and the Department of Homeland Security are among the parts of the government that will not remain funded if the shutdown occurs, much of these agencies will remain open because they provide security functions.

At Justice, large parts of the Federal Bureau of Investigation, the Drug Enforcement Administration, the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Bureau of Prisons and US attorneys' offices will remain open. Special counsel Robert Mueller's office will remain open as well, because it is funded with a permanent indefinite appropriation, according to the agency's shutdown plan.

At the Department of Homeland Security, about 55,000 Customs and Border Protection employees, about 55,000 Transportation Security Administration workers, about 44,000 Coast Guard employees, about 6,000 Secret Service employees and about 17,600 US Citizenship and Immigration Services workers will remain on the job through a shutdown.

Support staff, such as IT workers, necessary to support those whose work is essential will also be called in.

When would federal workers see the effects?

The holiday season is likely the worst time for federal workers at the nine departments.

While they will be paid for work performed before the shutdown, paychecks will not be cut while government agencies are closed. In past government shutdowns, Congress has often passed a bill to back-pay furloughed federal employees for the time they were not paid during the shutdown, but that is never a guarantee. Congress would have to pass a similar measure for furloughed federal employees to receive money lost during this shutdown. Contractors who work for the federal government may not be so lucky.

Office of Management and Budget guidelines also call for canceling paid vacation time that was scheduled over the holidays -- meaning many federal workers who took time off may see smaller paychecks.

The government would still process employee paychecks for the pay period ending on Saturday, although it wouldn't include pay for that day, because of the shutdown on Friday night. Employees' next paychecks would come after the government reopens.

Other government services may not be available, though.

The National Park Service and the Forest Service, for example, generally lock up visitor centers and restrooms, and have only minimal staff, such as law enforcement, on hand.

Unlike some past government shutdowns, this is a partial shutdown. Lawmakers approved funding for the other departments, such as Defense, earlier in the year.

Yes, Virginia, there is a Santa Claus tracker

The Santa Tracker run by the North American Aerospace Defense Command, or NORAD, will remain online.

"Military personnel who conduct NORAD Tracks Santa are supported by approximately 1,500 volunteers who make the program possible each and every year," the agency says.

In the event of a government shutdown, NORAD will continue with its 63-year tradition of NORAD Tracks Santa on Dec. 24. Military personnel who conduct NORAD Tracks Santa are supported by approximately 1,500 volunteers who make the program possible each and every year. pic.twitter.com/fY0oyjrdDc — NORAD & USNORTHCOM (@Norad_Northcom) December 21, 2018

The Polar Express railway near the Grand Canyon will continue to run, because it is operated by a third-party company rather than the National Park Service.

And Santa and his llamas -- yes, llamas -- are not canceling plans to visit the Olympic National Forest on Christmas Eve, where he will read to children at the Lake Quinault Lodge fireplace.