The Unite union has claimed “strong support” for the first day of a 72-hour strike by British Airways cabin crew.

Union members of the airline’s mix fleet cabin crew formed picket lines at Heathrow to protest over “poverty pay”.

Shadow chancellor John McDonnell, shadow business secretary Clive Lewis and Unite general secretary Len McCluskey also turned out at Heathrow.

The three-day strike, which started yesterday, is the second wave of industrial action against BA in as many weeks following the Heathrow-based mixed fleet cabin crew staging a stoppage on January 10-11.

The airline maintained its stance in the face of the latest walkout, saying that all passengers will be able to fly to their destinations despite the action.

BA expects to operate 99% of flight from Heathrow over the three days with a small number of short-haul flights being merged.

McCluskey said: “It was fantastic to see such strong support for our members in British Airways mixed fleet at Heathrow. Their courage and spirit in their fight for decent pay is undimmed despite the shamefully confrontational stance of British Airways.

“British Airways should be under no illusion about their determination to see movement on poverty pay. Mixed fleet cabin crew work tirelessly for pennies to provide a world class service and play a vital role in making British Airways a success.

“I urge British Airways to heed the anger of its mixed fleet cabin crew and work with Unite to address its pitiful levels of pay which force people to take second jobs to make ends meet.”

A spokeswoman for British Airways said: “Mixed fleet cabin crew pay and reward is in line with cabin crew at our competitor airlines. New cabin crew in their first year working full time at British Airways will receive more than £21,000 based on pay, allowances, incentive and bonus.

“We have offered an independent audit of our pay data over the last 12 months to support our statement that mixed fleet cabin crew all earn more than £21,000. The pay data shows that the range of earnings paid out to full-time mixed fleet crew between Sept 1 2015 and Aug 31 2016 was £21,151.35 – £27,356.30.

“We regularly recruit for mixed fleet cabin crew and we have lots of interest. In 2016 we received 31,000 applications for 2,000 cabin crew roles. We have more than 1,000 successful candidates who are due to participate in one of our training courses between now and March 2017.

“Last year, 20 per cent of our new Mixed Fleet entrants came from other airlines.”