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Air travel disruptions continued on Wednesday, and even though lawmakers are in Washington to vote on a deal that may end the , officials warned that delays and cancellations may persist. 

The Department of Transportation on Wednesday night announced that 6% of scheduled flights at  will remain canceled on Thursday, rolling back the initial plan to increase cancellations to 8% on Thursday.

Secretary of Transportation Sean Duffy said there has been a decline in air traffic controller callouts since the weekend. He said it's a good sign that airlines may soon be able to resume normal operations.

"The FAA safety team is encouraged to see our air traffic control staffing surge, and they feel comfortable with pausing the reduction schedule to give us time to review the airspace," Duffy said in a statement. "The data is going to guide what we do because the safety of the American people comes first."

More than 900 U.S. flights had been canceled as of 8 p.m. ET on Wednesday, according to data from the tracking site FlightAware. Another 2,203 flights were delayed, though not all of those delays were due to staffing.

Tuesday had  than previous days. Air traffic control towers reported minimal staffing shortages with only 11 staffing triggers, or times when the air traffic controller levels fell below planned minimums, compared to the 81 that occurred on Saturday. On Wednesday, there were four staffing triggers.

But even once the government reopens, reversing the flight cuts will not be immediate, Duffy said on Tuesday. The process may happen gradually, as the cuts themselves were phased in, he said. Duffy said he and FAA safety officials would look at relevant data, including pilot complaints, incidents where planes fly too close together, and runway incursions before reversing any of the cuts. 

Delta CEO Ed Bastian told CNBC that he believed the airline's operations would normalize shortly after the end of the shutdown. 

The House passed a bill to end the shutdown on Wednesday, and it now will head to President Trump's desk. The shutdown will end once Mr. Trump signs the bill. 

Delta had 2,500 cancellations in recent days, which Bastian said was a "crazy amount" that had cost the airline significantly. Travelers should be able to fly as scheduled for Thanksgiving as long as the shutdown ends soon, Bastian said.  

"We're going to be OK for Thanksgiving. We're going to be OK," he said. "We got to get the vote done, and so we're counting on Congress doing their job and making that happen. But Thanksgiving will be fine." 

The uncertainty is leaving flyers anxious. 

"We're just hoping and praying for the best," said Marlyn Mayo, who was flying from Washington, D.C., to Dallas-Fort Worth in Texas.