Members of the Unite union working for BA’s Mixed Fleet operation at Heathrow are walking out on Tuesday 10 and Wednesday 11 January in a dispute over what the union claims are “poverty pay” rates.

Around 4,500 passengers will find their flights to and from Heathrow are no longer operating. Flights from Gatwick, London City and Stansted are unaffected.

The daily 5,360-mile link to San Jose, serving Silicon Valley, has been cancelled on both strike days. Passengers are being offered seats on other BA flights to San Francisco, which is about 40 miles away.

Other cancellations are on routes where there are multiple daily services. On Heathrow-Philadelphia, for example, one of the two daily departures for Wednesday has been grounded.

The axed flights represent 3 per cent of BA’s total schedule of 1,600 services on the two days.

Passengers booked on the cancelled flights are being offered the chance to travel to the same destination on the same day, on one of the flights that is operating, or to rebook for another date within the next two weeks.

Alternatively, they can switch to a nearby destination, or claim a full refund.

Mixed Fleet began in 2010 after a long and bitter dispute involving BA cabin crew at Heathrow. New recruits are employed on inferior terms compared with longer-serving staff. They are currently deployed on around 50 long- and short-haul routes from Heathrow.

The plan is that Mixed Fleet will take over more services, as staff numbers in Euro Fleet and Worldwide Fleet – made up of longer-serving staff – dwindle.

Unite says pay rates for Mixed Fleet are so poor that safety is being jeopardised, with some staff “sleeping in cars between flights because they could not afford the petrol to get home”.

A Unite spokesperson said: “It should be to the company’s eternal shame that they, the UK’s national carrier, are making billions while their cabin crew, responsible for maintaining a safe environment, are working while sick and without adequate rest.”

British Airways maintains that its pay rates are competitive with the rest of the industry and says it is “available for further dialogue” with the union.