Portland International Jetport is warning passengers to anticipate significant flight cancellations as the Federal Aviation Administration reduces air traffic by 10% across 40 major airports to maintain safety during the ongoing government shutdown.

FAA officials announced a “proactive” plan Wednesday to trim airline schedules by 10% at 40 “high-volume traffic markets.” The thinning of more than 4,000 daily flights is expected to start at 4% Friday and gradually increase.

That plan was confirmed Thursday night, and flights will be reduced by 6% Tuesday, 8% by Nov. 13 and 10% by Nov. 14.

The list of the affected airports released Thursday night includes Boston Logan International Airport.

Officials at Logan did not respond to a request for information about flight impacts there Thursday afternoon.

While the jetport is not on the list of affected airports, the vast majority of its flights go to and from 15 airports on that list, jetport officials said.

“While the jetport is not one of the 40 airports with a restriction implemented, 97% of our flights are going to or from restricted airports and we will certainly have flight delays and cancellations as this shutdown continues,” Airport Director Paul Bradbury said in a statement Thursday night. “Each of our airline partners is reviewing their schedules and will be making operational decisions to meet the flight restrictions.”

Over the next two weeks, 1,016 of the jetport’s 1,044 scheduled flights are to or from airports that are being restricted.

As of Thursday night, more than 840 flights scheduled for Friday had been canceled nationwide, and an additional 450 flights scheduled for Saturday were canceled, the jetport said in its statement. While none of those flights are from Portland, the jetport’s statement notes that does not mean customers’ connecting flights at other airports won’t be delayed or canceled.

The jetport is encouraging passengers to check their flight status before heading to the airport. Airlines serving the airport have issued advisories that allow passengers to change flights to later dates or receive refunds if flights are canceled, the jetport said in its statement on Thursday.

Each airline is formulating its own plan to accommodate the 10% mandate, according to the notice on the jetport’s website. Airlines that serve the jetport are American Airlines, Breeze Airways, Delta Air Lines, JetBlue Airways, Southwest Airlines and United Airlines.

The cutback stands to impact thousands of flights nationwide because the FAA directs more than 44,000 flights daily, including commercial passenger flights, cargo planes and private aircraft.

“I’m not aware in my 35-year history in the aviation market where we’ve had a situation where we’re taking these kinds of measures,” FAA Administrator Bryan Bedford said at a news conference.

Air traffic controllers have been working unpaid since the shutdown began Oct. 1, and most have been on duty six days a week while putting in mandatory overtime. With some calling out of work due to frustration, taking second jobs or not having money for child care or gas, staffing shortages during some shifts have led to flight delays at a number of U.S. airports.

Citing increased staffing pressures and voluntary safety reports from pilots indicating growing fatigue among air traffic controllers, Bedford said he and U.S. Transportation Secretary Sean Duffy did not want to wait until the situation reached a crisis point.

“We’re not going to wait for a safety problem to truly manifest itself when the early indicators are telling us we can take action today to prevent things from deteriorating,” Bedford said. “The system is extremely safe today and will be extremely safe tomorrow. If the pressures continue to build even after we take these measures, we’ll come back and take additional measures.”

He and Duffy said they planned to meet with airline executives to determine how to implement the reduction in flights before the list of the affected airports was released sometime Thursday.

Staff Writer Drew Johnson contributed to this report, which also contains reporting from the Associated Press.