After US flights were suspended on Wednesday, normal air traffic operations are gradually returning to the US, according to the Federal Aviation Administration (FAA).
It comes after an issue with the system that warns pilots of potential dangers along flight paths.
Although more delays are anticipated owing to a backlog of flights, the FAA had previously stated that planes would start to take off again by 0900 ET (1400 GMT).
From Denver to Atlanta to New York City, airports all throughout the country were impacted.
More than 6,700 flights into and out of the US were delayed as of Wednesday morning (east coast time), and more than 1,000 planes were canceled.