Australia's Qantas Airways Monday extended its European flight cancellations into Wednesday and warned travel would remain difficult for "some days" even after volcano-hit services resume.

A spokesman said two Wednesday flights from Bangkok and Hong Kong to London had been axed, and warned that Tuesday's schedule to and from Europe was also likely to be wiped out by the freak cloud of ash from a volcano in Iceland.

"We're doing our best not to create any expectations that this is going to improve as of tomorrow our time," the spokesman told AFP.

"The indications still are that the airspace closures are going to stay in place for a period still, which means that we will be forced to make further cancellations."

About 10,000 Qantas passengers have been hit by the lockdown in services since Friday. The airline has offered free trips back to Australia for people stuck in Asian cities after their onward flights to Europe were axed.

However, the airline warned disruption would continue even after flights resume as it clears a backlog of thousands of passengers.

"Qantas will be doing everything to meet passenger needs once flights into Europe are able to resume," a statement said.

"However access to UK and European airports will be difficult due to the backlog of flights from around the world. This situation would be likely to continue for some days."