Most flights between Australia and New Zealand, however, remained grounded due to the drifting cloud of fine grit, which can damage airplane engines.

Airlines started flying a backlog of thousands of stranded passengers to and from Australia’s second—largest city on Monday after an ash cloud from a Chilean volcano began to clear after forcing hundreds of cancelations.

Most flights between Australia and New Zealand, however, remained grounded due to the drifting cloud of fine grit, which can damage airplane engines.

Several flights to and from the south-eastern city of Melbourne, the island state of Tasmania and New Zealand were cancelled on Sunday after the ash moved across the Pacific from Chile, where it has been spewing from the Cordon Caulle volcano since June 4.

In total, more than 55,000 passengers have been stranded by the disruptions, which came amid a three—day holiday weekend in Australia.

The cloud moved away from Melbourne on Monday afternoon, though, and national carrier Qantas and its budget subsidiary Jetstar resumed flights into and out of the city. Melbourne—based Tiger Airways became the last airline to resume Melbourne operations on Monday evening, company spokeswoman Vanessa Regan said.

Qantas estimated it could take 24 to 48 hours to clear just the Melbourne backlog.

Both Qantas and Jetstar continued to ground flights from the Australian mainland to Tasmania and New Zealand, citing the danger ash poses to engines.

The Australian air force ignored the danger to fly stranded Tasmanian lawmakers to the national capital Canberra in a jet late Monday to attend parliamentary sittings, the government said in a statement. The government holds a single seat majority in the House of Representatives so any absences could bring it down.

Virgin Australia cancelled flights on Sunday but started flying out of Melbourne, Tasmania and New Zealand again early Monday morning with a reduced schedule, flying below the cloud.

National carrier Air New Zealand never suspended service, instead choosing to divert flights and alter altitudes.

Qantas rejected flying below the cloud.

“This is about Qantas safety standards and procedures in place. We want to assure the safety of crew, the safety of our passengers and ultimately the safety of our airlines,” said Olivia Wirth, a Qantas spokeswoman. “So until such time that we get greater clarity on the ash cloud and until it removes, we will not operate services.”

New Zealand’s Civil Aviation Authority had some good news for airlines flying below the cloud. It said it was now safe for planes to fly up to 27,000 feet (8,000 meters), up from 20,000 feet (6,000 meters).

The plume of ash could disrupt travel for the next several days, according to Airservices Australia.

Flights in the South American countries of Chile, Argentina, Uruguay and Brazil were grounded for some days following the eruption.

The flight warnings and disruptions come 14 months after air traffic was grounded across Europe after the eruption of Iceland’s Eyjafjallajokull volcano.