Air traffic operations are beginning to resume following the outage that grounded millions of flights in the US on Wednesday.
The Federal Aviation Administration (FAA) said that it's continuing the investigation into what caused the glitch.
Some domestic flights in the US were grounded due to a technical glitch with flight control systems, reports BBC.
The FAA said it is working to fix a problem with the system that alerts pilots to potential hazards
All flights currently in the air are safe to land, it said.
Departures at two airports have resumed but many flights will remain grounded until 09:00 eastern (14:00 GMT)
The White House said President Biden has been briefed and that there is no evidence of a cyberattack.
Bd-pratidin English/Golam Rosul
