The Federal Aviation Administration (FAA) is expected to furlough about 4,000 of its employees on Saturday, as the Senate on Friday failed to approve a controversial House-passed extension of taxes that help fund the FAA. 

Those taxes expire at midnight Friday, and FAA Administrator Randy Babbitt has already warned that without an extension, furloughs would start Saturday.  

"We are going to be forced to furlough valuable FAA employees unless this situation is resolved quickly," Babbitt said earlier in the week. "These employees do everything from getting money out the door for airport construction projects to airport safety planning and NextGen research."

Transportation Secretary Ray LaHood has stressed that essential personnel related to airport and air safety would not be cut. "I want to reassure the flying public that, during this period, safety will not be compromised," he said.

This week, Senate Commerce, Science and Transportation Committee Chairman Jay RockefellerJohn (Jay) Davison RockefellerSenate GOP rejects Trump’s call to go big on gun legislation Overnight Tech: Trump nominates Dem to FCC | Facebook pulls suspected baseball gunman's pages | Uber board member resigns after sexist comment Trump nominates former FCC Dem for another term MORE (D-W.Va.) said the partial shutdown would halt all activities funded out of four accounts. This includes a $3.5 billion fund for infrastructure projects that he said supports 150,000 jobs per year.

Rockefeller also said the FAA estimates it could operate air traffic and support services through mid-August, but said operating this way would likely require the FAA to reduce services to smaller regions so it can focus on "primary traffic."

Despite LaHood's statement, Rockefeller added that operating this way can quickly have safety implications, and also slows technology upgrades.

The House on Wednesday approved an extension of FAA taxes until Sept. 16, but that extension included language that would prohibit federal subsidies from going to three small airports in Montana, Nevada and New Mexico because tickets there are subsidized at more than $1,000 per ticket.

The House extension includes language eliminating subsidies to 10 small airports because they are within 90 miles of a medium or large airport. However, this language is also in a Senate-passed bill.

As a result, House Republicans argued Wednesday that the failure of the Senate to take up the House bill by Friday would mean a partial FAA shutdown would be the fault of Democrats who are protesting the addition of language that affects just three small airports.

"It will be the responsibility of the other body who does not take this up and pass it," House Transportation and Infrastructure Committee Chairman John Mica (R-Fla.) said. "They will be furloughing people and putting people out of jobs."

Mica said Friday that it is "unbelievable" that the Senate left Washington without extending FAA taxes. "In light of the nation’s pending financial disaster and soaring deficits, they couldn't find a way to cut even a few million dollars by accepting this minor request to reduce outlandish subsidies," he said.

A spokesman for Senate Majority Leader Harry ReidHarry Mason ReidAmendments fuel resentments within Senate GOP Donald Trump is delivering on his promises and voters are noticing Danny Tarkanian wins Nevada GOP congressional primary MORE (D-Nev.) said the GOP bill would needlessly hurt small airports, like the one in Reid's home state in Ely, Nevada.

"This is nothing less than a direct assault by Washington Republicans on already underserved rural communities -- not only in Nevada, but across the country," said Spokesman Zac Petkanas. "The reckless House approach will not only shut down the FAA, but it could also hurt Congress’ ability to successfully complete work on a long-term FAA reauthorization."

Rockefeller on Thursday said House Republicans are to blame because they chose to do something other than a clean extension.

"[T]he House passed an FAA extension that, unlike the 20 previous FAA extensions, included changes to FAA policy that have not been agreed to in both chambers," he said. "This move will shut down the FAA beginning tomorrow at midnight if we do not reach agreement on a sensible path forward to pass a clean FAA extension."

-- This story was updated at 2:42 p.m. to add comments from Reid's spokesman and again at 3:35 p.m. to add comments from Mica.