Airlines canceled thousands more flights Saturday as they recovered from Friday's nationwide ground stop, but the FAA said schedules should be back to normal by the end of Sunday.

FAA Administrator Bryan Bedford said he expects 4,000 to 5,000 of the roughly 41,000 flights scheduled Saturday to be canceled. More than 4,000 U.S. flights had been canceled as of 10:50 a.m. ET, according to FlightAware. "I do think the worst is behind us," Bedford said, and he apologized to travelers.

The FAA halted departures nationwide for more than four hours Friday, the longest ground stop since the Sept. 11, 2001, attacks. About 12,000 flights couldn't be completed, Bedford said.

Transportation Secretary Sean Duffy said the outage began while L3Harris Technologies, which ru...