The Italian volcano, which at 3,330m (10,925 ft) high is Europe's tallest and most active, began erupting overnight, officials said cited by Skynews.
Although the lava flow subsided before dawn, ash was still coming from one of the craters.
No flights will go in or out of Catania, a popular tourist destination, until 8pm (6pm, UK time), the airport said on X, formerly known as Twitter, and earlier on Monday, the airport itself was temporarily closed.
Several British Airways, Ryanair, easyJet and KLM flights have been cancelled, delayed, or diverted to other airports on the island.
Catania International Airport said: "Due to Etna's eruptive activity and fallout of volcanic ash, flight operations are suspended until 8pm."
TM/PR