The volcanic ash cloud over the eastern part of Australia is costing the tourism sector more than $10 million a day, an industry group says.

Tourism and Transport Forum chief executive John Lee said the return of the ash cloud was causing havoc across the country, after the major airlines suspended services in and out of the key hubs of Sydney and Melbourne.

In our estimate for the wider tourism industry along the east coast and bottom part of Australia, the daily impact will be over $10 million, Mr Lee said on Tuesday. This is nearly the straw that will break the camel's back for this industry, he added.

A Qantas spokeswoman said earlier on Tuesday the delays were serious, but the airline did not yet have a figure on costs.

Tens of thousands of travellers have been stranded as the ash from Chile's Puyehue volcano made its second trip through Australian airspace. On Monday, flights into and out of Adelaide were cancelled and by Tuesday, the cloud cancelled arrivals and departures in the country's two biggest cities, Melbourne and Sydney.

The ash cloud is actually larger than it was on its first trip to Australia at a whopping 2000km long with a base sitting low at about 6km.

It makes it impossible for airlines to fly underneath it or around it, it's just too big essentially,'' said Civil Aviation Safety Authority spokesman Peter Gibson.

Airlines warned it could take days, even with extra flights, to help the backlog of stranded travellers.

428 flights were cancelled across the country and all international flights due to arrive in Melbourne and Sydney were diverted to Brisbane. Nearly 50,000 travellers have been affected these past two days.

Qantas will ground Melbourne and Canberra flights on Wednesday until 11am, Sydney flights until 2pm, and Hobart flights until 5pm.

Adelaide flights were to resume in the morning, but trans-Tasman flights to New Zealand were to be grounded from 7am until further notice.

Jetstar, which on Tuesday axed more than 70 flights, affecting 9000 passengers, is cancelling all Melbourne flights until 11am, Sydney until 2pm, Tasmania until noon, and Newcastle services until 2pm Wednesday.

Tiger stopped flying on all its Australian routes on Tuesday, cancelling about 60 flights affecting 9000 passengers. On Wednesday, it is cancelling 14 flights, including some Melbourne, Sydney, Brisbane and Adelaide services, mainly in the morning.

Experts have warned the ash cloud from the erupting Chilean volcano, which has already caused 10 days of chaos, could return again.

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