Travellers' anticipation at snaring a $240 Melbourne to London fare on AirAsia has turned to anger among those who missed out.

The rock-bottom fares advertised by AirAsia yesterday went on sale at 2am this morning but were sold out within an hour.

Fairfax has received heated calls today from disappointed travellers complaining about AirAsia, angered that they could not access the sale fares — offers that were still being promoted on AirAsia's website at 2pm today.

One disappointed customer, whose booking ended up costing thousands of dollars — rather than hundreds — has vowed to complain about AirAsia to the Australian Competition and Consumer Commission.

But a public relations agent for AirAsia defended the sale, saying that among the various fares in the sale as many as 4000 seats from Australia (exiting Melbourne, the Gold Coast or Perth) to its Kuala Lumpur hub — the first leg of the trip to London — were offered.

Approximately 1000 discount seats were offered on the Kuala Lumpur-London sector. All have been sold, too, Air Asia's spokesman said.

"There were a lot of people waiting online last night," the spokesman said.

"It's been a popular sale."

Another 1500 sale seats from Australia to KL were added today in response to customer demand but they too had probably been snapped up by now, he said.

Travellers today complained that the sale fares were still being advertised on the AirAsia website, despite the fares having sold out.

The airline was in the process of uploading a "sold out" banner on its site, and had already pulled web sale ads on third-party websites, the spokesman said.

In Kuala Lumpur yesterday, no sooner had AirAsia announced its ultra-low sale fares than the carrier's chief executive Tony Fernandes advised the Malaysian stock exchange of the parent company's intention to spin-off its subsidiaries.

It intends to list its long-haul operation, AirAsia X, as a separate entity, rather than keeping the airline under the one corporate umbrella of its parent company AirAsia Berhad.

AirAsia X would be offered for listing, subject to market conditions, in the second half of next year, he said.

The aggressive manoeuvres being played out in the skies underlines the pressure being felt by carriers such as Virgin Blue, which has warned investors that its profits are being eroded in the market by low-cost carriers.

Virgin Blue's new chief executive John Borghetti seeking to change the trajectory of the airline group's offerings to chase lucrative government and business travellers, rather than rely on bread-and-butter leisure travellers.

Jetstar's direct Singapore-Auckland flights announced today add more pressure on the proposed tie-up between Virgin Blue and Air New Zealand on New Zealand services.