The Federal Aviation Administration on Friday halved the number of flights that airlines have to cut from their schedules at 40 busy airports as the country's aviation system continues to recover from the longest government shutdown ever.

The agency said that beginning Saturday airlines will only have to cut 3% of their flights instead of the current 6%.

The number of canceled flights peaked last Sunday when nearly 3,000 flights — or about 10% — were cut as a result of the FAA order combined with continued shortages of controllers and severe weather in parts of the country.

By Friday afternoon, the flight tracking website FlightAware showed just 159 cancellations for Saturday in the U.S.

The rollback comes amid improved staffing levels at air traffic controller facilities after the record 43-day shutdown ended Wednesday night, the FAA and Department of Transportation said, adding that they will continue to monitor the situation throughout the weekend and evaluate whether normal operations can resume.

Transportation Secretary Sean Duffy has repeatedly said safety metrics must improve before the order is lifted entirely.

The unprecedented order, in place since Nov. 7, has affected thousands of flights. The head of the FAA said troubling data showed the measure was needed to ease pressure on the aviation system as the shutdown entered its second month and controller absences rose. Unpaid for more than a month, many controllers cited financial strain and the need to take on side jobs.

The flight cuts started at 4% and later grew to 6%. The FAA originally had a 10% target, but officials held off on further rate increases because they said more controllers were coming to work amid news that Congress was close to reaching a deal to end the shutdown.

Air traffic controllers missed two paychecks during the impasse.

Duffy hasn’t shared the specific safety data that prompted the cuts, but he cited reports during the shutdown of planes getting too close in the air, more runway incursions and pilot concerns about controllers’ responses.

How long it will take for the aviation system to stabilize is unclear. The flight restrictions upended airline operations in just a matter of days. Many planes were rerouted and aren’t where they’re supposed to be. Airlines for America, the trade group of U.S. airlines, warned there could be residual effects for days.

Some experts predicted the problems could linger longer but airline executives were optimistic that flying could quickly return to normal ahead of the busy Thanksgiving travel week.

The nationwide shortage of controllers isn’t new, but the shutdown put a spotlight on the problem and likely made it worse. Duffy said that by the end of the shutdown, 15-20 controllers were retiring daily and some younger controllers were leaving the profession.