Qantas and Jetstar have resumed flights in and out of Melbourne after volcanic ash from Chile caused chaos at airports across Australia and New Zealand. The airlines' services to Tasmania and New Zealand, however, are still grounded, leaving thousands of passengers stranded and there are concerns the ash cloud is heading towards Adelaide. Qantas said 20,000 passengers and 100 flights had been cancelled over the weekend. While Qantas and Jetstar move to clear the backlog of stranded passengers, Tiger Airways is still waiting to get its fleet off the ground saying flights will not resume until at least 5:00pm. Tiger has also cancelled flights from Perth to Melbourne until Wednesday. Virgin was the first to resume domestic flights out of Melbourne at dawn and is now flying to Tasmania and New Zealand. New Zealand's Civil Aviation Authority earlier said the country's airspace may be affected for at least a week, given the Chilean volcano is still erupting. Gordon Jackson from the Volcanic Ash Advisory Centre said the plume is likely to move away from Victoria over the next 18 hours.