More than 5,000 US flights were cancelled or delayed on Friday, in the first day of new mandates forcing airlines to reduce air traffic during the government shutdown.

The new rules went into effect on Friday at 40 of the country's biggest airports to ease pressure on air traffic controllers and other federal workers reporting to work without pay amid the historic federal funding impasse.

Essential employees have been calling in sick or taking side jobs to make ends meet since the shutdown started last month.

To manage staffing shortages, the Federal Aviation Administration (FAA) issued an emergency order mandating a 4% cut to flights - which will rise to 10% by the end of next week.

The mandate - impacting major travel hubs in New York, Los Angeles, Chicago and Washington DC - came down as air traffic controllers had been reporting fatigue during staffing shortages as they work to ensure that US airspace remains safe for passengers, according to the FAA.

essential workers, air traffic controllers are required to continue working without pay during the shutdown - which has become the longest ever in US history.

Continuing to work without pay for more than a month has led many to become ill with stress and forced others to take on second jobs to keep food on the table, unions for the employees have said.

Transportation Secretary Sean Duffy told the BBC on Friday that the flight cut mandate has not yet affected international travel due to international agreements that the US has to abide by.

But the chaos at airports could be just beginning. Duffy said in an interview with Fox News that cuts to flights could hit 20% if the government shutdown carries on and air traffic controllers continue to miss work.

Nick Daniels, the president of the National Air Traffic Controllers Association, said the controllers are being used as political pawns in the political standoff.

"We know the problems are going to get worse. They're going to increase, and anything that helps improve safety, we 100% stand by ensuring the safety of the American flying public," he told CNN.

Daniels said air traffic controllers are going to continue to show up and "do the job".

"We are going to do everything we can, but what we can't do is somehow, suddenly put money in our own pocket," he said. "We need Congress to open the government."

Beyond air travel, the shutdown has caused unprecedented disruptions across the country, including a pause in funding for food aide programmes.

Stressed travellers and cancel messages lit up flight status boards on Friday as the emergency order took effect.

As the mandate upended domestic air travel, several airlines began issuing advice for customers. Many carriers - including Delta, United and American Airlines - offered re-booking or change-fee waivers or full refunds, even to those whose flights were not impacted.

Joe Sullivan said he was already in an Uber to Reagan National Airport in Washington DC when he received the notification that his flight to Atlanta, Georgia, was cancelled. He was on his way to his cousin's wedding.

That city's airport, Hartsfield-Jackson Atlanta International Airport, is often cited among the world's busiest and is a hub for Delta Airlines. It was one of the 40 airports that the US government selected to reduce flights.

"I ended up getting rebooked, but not until a flight that's more than 12 hours later the next day," Mr Sullivan said.

He thinks he might still be able to make it to the wedding, landing two hours before the ceremony begins. Other planned activities, though, he will miss.

"I was hoping to catch up with family down there tonight so [it's] a huge inconvenience in that regard," he added. "All I can do is just go home and just sit on the couch and wait for my flight to take off tomorrow."

Some at the airport were plotting other ways to get to their destinations. One woman told the BBC she bought a $300 train ticket - a trip that will take seven hours - in case her hour-long flight is cancelled.

Fellow traveller, Ndenisarya Meekins, told the BBC that she had to rebook her flight due to her planned trip to New York getting cancelled.

"We have a lot of plans in New York, so it would have been a little bit of a catastrophe if we weren't able to make it up," she said.

Ms Meekins said travelling at this time feels "nerve-wracking" because of the air traffic controller shortage.

"We're trusting that we have what we need to be safe," she said. "You think about these folks that have been working also without pay. We're going to go through security right now, and these are TSA agents who have been going through this process without pay and your heart goes out to them."

For Ariana Jakovljevic, the shutdown-induced travel panic is only one part of the funding gridlock's impact on her life. She is a federal worker who has not been paid because of the shutdown.

"I just graduated college. This is my first real job. I thought I had the golden ticket. I keep hoping stuff will get taken care of," she said.

With air traffic controllers already stretched thin by pre-existing staff shortages, traveller Ben Sauceda said working without pay is not ideal.

"I'm entrusting my life, every time I'm flying, with air traffic controllers," Mr Sauceda said. "They're phenomenal ? but right now I'm putting [my life] into the hands of people who aren't getting paid, and that puts a stress on them; when they're trying to figure out how to feed their families.

"We're asking them to be top notch, to protect us," he added. "The stresses that are put on them are incredibly hard.

"The government needs to figure this out."

It remains unclear when the 38-day shutdown will come to an end - but there has been movement on Capitol Hill with members of Congress.

For the first few weeks of the shutdown, there were few, if any, negotiations happening between Republicans and Democrats.

Now, conversations are happening and both sides seem to think a deal could come to fruition.

On Friday, Democrats offered a potential funding bill. The chances of it passing are slim, though, because it does not have Republican support. A total of 60 votes are needed in the Senate to pass a funding measure and the chamber is split with 53 Republicans and 47 Democrats.

Since the shutdown began, members of the Republican-controlled US Senate have repeatedly voted - to no avail - in favour of the same short-term funding bill to reopen the government with no luck.

Democrats have refused to support the short-term measure on government funding unless Republicans agree to extend healthcare subsidies for low-income Americans. Republicans have resisted, accusing Democrats of holding the government hostage over unrelated policy priorities.

Senate Majority Leader John Thune, the chamber's top Republican, told reporters on Friday that work would continue over the weekend to come to a deal. He said senators were instructed to stay in town in case there was legislation to vote on.

The House of Representatives has been out of session since the start of the shutdown.

In recent days, President Donald Trump has started suggesting the shutdown could end by doing away with the Senate's filibuster - a long-standing rule that only requires 60 of the 100 members to approve most legislation.

Removing the rule would allow Republicans to pass a funding bill without Democratic support.

But few senators, Democrat or Republican, support the president's proposal.

That did not stop Trump from pushing for the end of the filibuster again on Friday.

"The United States Senate should not leave town until they have a Deal to end the Democrat Shutdown. If they can't reach a Deal, the Republicans should terminate the Filibuster, IMMEDIATELY, and take care of our Great American Workers," he wrote on Truth Social. (BBC)

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