British Airways cabin crew who fly both long and short haul flights will strike for another two weeks during the summer holidays.
It means they could now strike until the end of the month, prolonging their action from 16 August and taking in the bank holiday on 28 August.
Those taking part have joined BA since 2010. It was their 58th day of strike action on Thursday. If a deal is not reached, their protest could cover most of July and August.
The Unite union has described an offer by BA to reinstate travel concessions for workers who have taken action as “half-hearted”.
Unite national officer Oliver Richardson said that “in robbing striking workers of hard-earned bonuses the airline has sought to sow division”.
Image: British Airways planes at Heathrow Airport
He said: “The airline needs to get around the negotiating table and start recognising that punishing low-paid workers fighting for fairer pay is no way for a ‘premium’ airline to behave.”
Mr Richardson claimed “last week’s massive profits” showed BA could afford to look at pay.
The union claims its action has forced BA to spend millions of pounds on leasing aircraft.
“As we have done in previous periods of industrial action, we will ensure our customers reach their destinations,” BA said in a statement.
“More than three months ago, Unite agreed that our pay deal was acceptable, but have since refused to ballot their members on it.
“Last week, we took the significant step of offering to return staff travel to crew who had been on strike, which was the biggest outstanding issue in the dispute, in order to bring the dispute to an end.
“Unite has now chosen to reject this offer and call yet more strikes.”
The airline said it confirmed earlier this year that the cabin crew would be eligible for the 2017 bonus.