As Republicans scramble on Capitol Hill to get a new government funding agreement passed, many federal workers are now in limbo waiting to see how a government shutdown would impact them with the holidays right around the corner.
Based on past government estimates, some 3.5 million federal workers could go without paychecks this holiday season until an agreement is passed — many of them, like airport security officers, will be required to show up to work anyway. Others could be told to stay home and not work.
A payroll schedule for the U.S. General Services Administration shows some federal workers would miss paychecks as soon as Jan. 3 if an agreement is not reached by then.
MORE: Government shutdown live updates: House plans to vote on new bill as deadline nearsFederal contractors are not required to work and are also not guaranteed backpay for the duration of the shutdown.
Since fiscal year 1977, there have been 20 funding gaps, lasting from as short as 1 day to 34 full days in length. If the government shuts down Saturday at 12:01 a.m., it would be the 21st shutdown.
Below is a small snapshot of the impact a shutdown could have on millions of Americans across the country.
The shutdown would come just as many Americans are traveling for the holidays -- during some of the busiest travel days of the year.
MORE: How a government shutdown could impact air travelThe shutdown could lead to longer security checkpoint wait times at the airports and impact hiring of air traffic controllers if the shutdown lasts for long.
The Transportation Security Administration says about 59,000 of the agency’s more than 62,000 employees are considered essential and would continue working without pay in the event of a shutdown.
TSA says the agency expects to screen 40 million passengers over the holidays through Jan. 2.
“While our personnel are prepared to handle high volumes of travelers and ensure safe travel, please be aware that an extended shutdown could mean longer wait times at airports,” TSA Administrator David Pekoske said on X.
Nearly 13,000 air traffic controllers would be expected to work without pay, and hiring and training new air traffic controllers would cease during a shutdown, according to the latest planning document from the Department of Transportation.
It's worth noting that air traffic controllers played a part in ending the government shutdown in 2019, when several workers called in sick on the same day, snarling air traffic. Then-President Donald Trump announced an agreement to temporarily reopen the government the same day.
Read more about the possible impact on air travel.
If there is a government shutdown after tonight the U.S. military’s military operations overseas and domestically will continue, but U.S. military service members won’t be paid during that time.
Some 1.3 million active-duty service members would still be required to work, but without pay until a funding agreement is passed. Typically, half of the 700,000 Defense Department civilian workforce would be expected to keep working without pay.
If a shutdown goes into effect, defense Department civilians will be given guidance to show up at their offices on Monday morning and they will have four hours to sign a memo that acknowledges they will not be working, and will then have time to set up their out-of-office emails and voicemails, and turn off their phones and laptops so they will be unable to work from home during the shutdown. If the employees happen to be on time-off during the shutdown they will be able to provide a digital signature of that memo and they will turn off their devices. They will also provide personal email addresses so they can be contacted once the shutdown is over.
Both U.S. military personnel and DOD civilians are guaranteed retroactive pay after the shutdown ends under the Government Employee Fair Treatment Act of 2019.
Generally, contractors are not required to work and would lose paychecks for the duration of the shutdown. Contractors who work for the Pentagon will continue to work if their contract is funded through the current year.
An estimated 60,971 employees with U.S. Customs and Border Protection and 17,575 employees with Immigration and Customs Enforcement would be asked to work without pay during a shutdown according to the latest planning document from the Department of Homeland Security.
Because they are considered “mandatory” spending, payments from Social Security and Medicare will continue to reach mailboxes, although agencies warn services could slow down.
The U.S. Postal Service also won't be impacted because it is an independent agency, and relies on its own revenue stream.
Given the shutdown would begin on a Saturday, many Americans would not really feel the impacts of a shutdown until Monday.
The National Park Service said they “remain hopeful that a lapse in government funding will not occur,” but if it does, “routine visitor services will be available through Sunday.” They are still reviewing the agency's contingency plan and working to determine specifics for individual parks.
The Smithsonian Institution, which operates 21 museums and the National Zoo in Washington, D.C., said it will use leftover funding to remain open to the public at least through Dec. 26, except for Christmas Day when all museums and the zoo are closed.
ABC News' Luis Martinez and Ayesha Ayi contributed to this report.