The walkout, organised by the Unite union, is being conducted by members the airline’s Mixed Fleet staff based out of Heathrow.
Unite said shadow chancellor John McDonnell would be joining cabin crew on picket lines at the London terminal today.
The 72-hour industrial action follows a two-day stoppage last week, which Unite said saw “hundreds of Mixed Fleet cabin crew stay away from work and mount picket lines” at Heathrow.
Unite national officer Oliver Richardson said: “British Airways needs to drop its confrontational stance which is causing so much anger and leading to plummeting morale among its mixed cabin crew.
“With British Airways’ parent company forecasting massive annual profits of around £2.3 billion, it is clear the airline can afford to recognise the hard work of its Mixed Fleet cabin crew by paying a proper decent wage.
“Rather than trying to bully workers and focusing its resources on leasing aircraft to cover striking cabin crew, British Airways should focus its energies on trying to resolve our members’ legitimate concerns over poverty pay.
“Unite urges British Airways to wake up to the deepening anger of Mixed Fleet cabin crew and start valuing their contribution by meaningfully engaging with Unite to address poverty pay.”
BA has said last week’s 48-hour walk-out had not disrupted customers, claiming more than 70% of Mixed Fleet crew had reported for work as normal.
In a statement the airline said: "We operated nearly 1,600 flights over the two days, as planned, and transported all 210,000 customers to their destinations.
"So it is bizarre, as well as regrettable, that Mixed Fleet Unite branch has announced further strike dates.
"We will again aim to ensure that all our customers travel to their destinations in this period and we will publish more details on Monday once we have finalised our contingency plans.
"Unite’s attempt to create uncertainty for customers and further division among its own members is completely without justification."
