BBC News - Antoinette Radford & Nadine Yousif & Brandon Drenon
US flight operations are back to normal, following a technical glitch that paused air travel on Wednesday, officials said.
Early investigations by the Federal Aviation Administration (FAA) suggest the glitch was caused by a "damaged database file".
More than 11,000 flights in and out of the US had been delayed and at least 1,300 were cancelled.
"We are seeing no unusual delays this morning," the FAA said.
A senior government official said a corrupted file caused the issue, affecting both the primary and backup systems of the FAA's Notice to Air Mission system, or NOTAM. Officials continue to investigate the issue, they said.
"At this time, there is no evidence of a cyber attack", the FAA said.