Sydney Airport resumed operations after air traffic control staff who were evacuated due to smoke were cleared to return to work.

Air Services Australia said departures at the nation’s busiest airport were running smoothly and all restrictions had been lifted.

Departures were grounded and arrivals were delayed after as many as 20 control tower staff were evacuated earlier Friday.

Sydney Airport is a hub for airlines including Qantas Airways Ltd. and Virgin Australia Holdings Ltd., which both said they were working to get flights back on schedule.