One of Sicily’s busiest airports has canceled more than 700 flights in the past week because of steady eruptions from Mount Etna, a volcano that has spewed millions of cubic yards of ash through eastern Sicily and its airspace.

Etna is one of Europe’s most active volcanoes, and its eruptions are frequent, said Salvatore Gambino, the director of a National Institute of Geophysics and Volcanology observatory, which is situated on the mountain. But he said the current spell, which began on Aug. 6, was unusual because of the “sustained and continuous emission of ash.”

Steady southeast winds have been blowing plumes of ash from one of the volcano’s central craters toward the international airport in Catania, a major port city at Etna’s base.

Since Friday, the airport has closed, reopened and re-closed its airspace, causing headaches for tens of thousands of travelers at the height of Italy’s summer vacation season, and just before Ferragosto, a national holiday that falls on Saturday.

Sicily’s regional government and the Catania airport authority have organized train and bus shuttle services for passengers whose flights are diverted to other Sicilian airports, including in Palermo and Trapani, on the island’s western coast.

Still, passengers have camped out at Catania’s airport and slept on luggage carousels, Italian news media reported. Sicily’s government said it had stationed volunteer teams at the airport to hand out water. Catania’s airport authority did not immediately respond to a request for comment.

Catania’s tourism office said it could not estimate how many tourists were stranded. “We are sincerely sorry for what is happening these days and for all the potential inconveniences that the situation on Etna is causing,” Lucia Caffo, the office’s head of tourist promotion and development, wrote in an email.

A Sicilian business association estimated that the disruptions could cost $15 million to $29 million in lost tourism revenue.

Mr. Gambino said it was “absolutely impossible” to predict how much more ash Etna would spew, for how much longer and where the wind would send it. As of Thursday, the volcano’s activity was holding steady, he said.

“It could end tomorrow, in a few days, in a week or in a month,” he said.