British Airways cabin crew have begun a five-day strike as part of their long-running dispute with the carrier.
It is expected that the latest strike is expected to hit flights to and from Heathrow airport.
In the long-running standoff between the two companies - which has already witnessed court orders, appeals and the storming of negotiations by protestors – the latest action comes as another financial blow to the company.
BA has accused Unite, the union representing the cabin crew, of failing to take up an offer of further talks, adding it was disappointed Unite had resorted to "negotiation through the media".
Earlier, Unite's joint general secretary Tony Woodley offered to call off the latest walkout if travel perks for cabin staff were reinstated.
But BA asserted it had already agreed to the measures once its deal was accepted in full.
Unite said the removal of travel concessions for members who went on strike in March is one of the central reasons behind the planned strikes.
BA said it plans to fly more than 60,000 customers a day during the strike, operating 60% of long-haul flights and 50% of short-haul services from Heathrow.
It added that all flights at London Gatwick and London City will operate normally.