Washington DC - US officials said Wednesday the scheduled capacity for flights was being cut by 10% from Friday in 40 busy air traffic areas of the country, with an ongoing government shutdown causing major staffing woes.

"There is going to be a 10% reduction in capacity at 40 of our locations," Transportation Secretary Sean Duffy told a news conference.

Federal Aviation Administration chief Bryan Bedford said the cuts would come at "40 high traffic environment markets."

Federal agencies have been grinding to a halt since Congress failed to approve funding past September 30, and on Wednesday, the shutdown officially became the longest in US history at 36 days and counting.

More than 60,000 air traffic controllers and Transportation Security Administration officers are working without pay, and the White House has warned that increased absenteeism could mean chaos at check-in lines.

Airport workers calling in sick rather than working without pay – leading to significant delays – was a major factor in Trump bringing an end to the 2019 shutdown.

Thanksgiving air travel is expected to set a new record this year, the American Automobile Association projected – with 5.8 million people set to fly domestically over the November 27 holiday.