Qantas has cancelled more than 40 flights over today and tomorrow, blaming industrial action by the airline's engineers.

Qantas said this morning that 30 domestic flights had been cancelled today and 14 tomorrow because of the flow-on effects of action by engineers over the past two days.

More disruption is expected on Friday, with engineers due to hold another rolling stoppage in support of their 5 per cent pay claim,

Qantas said the 43 flights cancelled today and tomorrow were predominantly Sydney, Melbourne and Brisbane domestic services and there were no international flight cancellations at this stage.

As a result of strikes on Monday and Tuesday there will be some flow-on effects on flights today and Thursday, ``including a number of cancellations," a Qantas spokeswoman said today.

"We're contacting all affected passengers and rebooking them on the next available flight. We expect this to be within 30 minutes of the original departure time in almost all cases."

Yesterday's strike action prompted the airline to cancel 35 domestic flights - about double the original estimate of 18 - and delay some international services.

Hundreds of passengers were stranded in Perth after a plane developed technical difficulties, which airline officials said were unrelated to the strike.

The Australian Licensed Aircraft Engineers Association said it would take industrial action on Friday and consider more next week unless Qantas lifted its 3 per cent pay offer.

But Qantas chief executive Geoff Dixon was last night maintaining his stance that he wold not negotiate while threatened by strike action.

The union's federal president, Paul Cousins, apologised for inconveniencing the travelling public but said the union wanted to "keep pressure" on Qantas.

"The ball is in Qantas's court. They can stop this dispute at any time by coming back to the table with a reasonable offer," he said.

Mr Cousins hit out at Qantas's moves to permanently increase the amount of critical maintenance work done offshore, including more checks being made in the US and London.

"The standards they abide to are certainly not up to the standards that we require here in Australia," he said.

"Our concerns are, if these safety levels are not met to the level at which they are in Australia, then what is to protect the Australian public?"

But Mr Dixon dismissed the claim as laughable, saying checks planned for Los Angeles and other ports would be supervised by Qantas engineers.

He said 15-20 per cent of Qantas engineering had been done offshore for 50 years and that the airline would not be in business if it could not get some engineering done overseas.

"I have the greatest respect for Australian engineers, particularly Qantas engineers, but it is laughable to think that British, American, Singaporean, Hong Kong and other engineers are not competent and well trained," he said.

Mr Cousins said the union had not received guarantees that a Qantas joint venture with Malaysia Airlines to provide airframe maintenance services in Kuala Lumpur would not be further used by Qantas to outsource work.

"We have not received a specific undertaking that they won't use Kuala Lumpur for heavy engineering," he said. Protocol required any outsourcing to be discussed at the highest levels, he said.

Mr Dixon said the strike would not push Qantas to send more work to the Malaysian joint venture.

"This action won't force us or motivate us to move more engineering offshore," he said. "We've never made that threat and we won't make it.

"What we're saying is that ... where we have downtime in LA, London or Hong Kong the A-checks, at any rate, we can get done there."

The Transport Workers Union is holding meeting of its airline members before finalising a Qantas wage claim.

Scott Connolly, the union's senior airlines official, said members would be seeking undertakings about job security, safety and the "appropriate use of outsourced labour".