British Airways has declared that the second strike is inflicting less financial and operational damage than the first, with losses of £5.5m a day compared to £7m of the original three-day strike. This puts the total cost of the two strikes by cabin crew at around £40m.

The announcement comes in response to claims by Unite that the seven days of industrial action would cost the UK flag carrier more than £100m, as well as what it called “self-inflicted trashing of its brand”.

The trade union meanwhile is raising £700,000 in a cash call on its membership to keep the strike going. The money is the equivalent of about two days’ pay for the 11,500 striking cabin crew.

The second round of industrial action, which is now in its fourth day in the current stoppage and its seventh this month, is costing Unite nearly £350,000 a day in strike pay.

Union officials said that the cash was likely to help finance a hardship fund for striking cabin crew who are struggling to cope on the £30 a day that Unite is paying them.

It is the first time since its formation in 2007 that Unite has raised such a levy to support a strike. “This is an unprecedented move and it shows that Unite is absolutely determined to give our members all the support they deserve in winning this battle against the BA bullies,” said Tony Woodley, Unite joint general secretary.

“We continue to search for a decent settlement in this dispute but cabin crew are not going to be driven back to work for lack of resources.”

Willie Walsh, BA chief executive, has toughen further his stance on strikers by withdrawing their travel privileges for strikers and capping maximum pay for trips on which crew were rostered.

BA also said it operated 83 percent of its long-haul programme last weekend and 67 percent of short-haul flights. That compares with a respective 78 percent and 50 percent for the previous weekend of strikes.