Qantas says its customers affected by a British Airways (BA) strike launched on Saturday will not be left stranded, with the company to arrange alternative flights.

Thousands of BA cabin crew began the three-day strike after last-ditch talks on a dispute over pay and conditions collapsed, leaving thousands of travellers facing chaos.

More than 1,000 flights are expected to be cancelled, followed by a potentially more damaging second walkout for four days from March 27 ahead of the busy Easter holiday period.

Passengers facing disruption include those travelling between Australia and the United Kingdom.

Qantas said BA indicated it plans to operate its daily flights between London and Sydney via Bangkok.

But the airline’s daily London-Singapore journeys have been cut, affecting an unknown number of Qantas passengers booked on those connecting services.

Qantas said its priority was to ensure those people were accommodated on its own flights or offered other alternatives.

“We have contacted affected customers … (and) have a fare waiver in place that allows people travelling during the strike period to change their booking without penalty,” a Qantas spokeswoman said.

“We will continue to liaise with British Airways regarding its plans for the second phase of its planned strike action and closely monitor what else we can do to minimise potential impacts on our customers.”

Qantas said all of its services between Australia and the UK will operate as scheduled.

BA said emergency plans to handle the strike were working well.

It plans to fly more than 60 per cent of passengers this weekend – about 49,000 people a day – despite cancelling many of its scheduled flights.

“Our main aim this week has been to give customers as much information as early as possible so that they take up one of the options we have offered them,” a spokesman said.

- AAP/Reuters