JOIN USBA warned that the unprecedented scale of the walkouts over a 23-day period would cause "extensive disruption for potentially hundreds of thousands of customers over a busy period."
The strike action, due to begin early next week, will also add to mounting costs for the struggling British flagship carrier in the wake of the volcano disruption and walkouts by BA staff last month.
Unite, which represents around 90 per cent of BA's 12,000 cabin crew, said it was forced to ramp up its actions in a long-running and increasingly bitter dispute over pay and conditions after BA turned down an approach by the union over the weekend.
The strike dates are May 18-22, May 24-28, May 30-June 3 and June 5-9 _ leaving just a day's breather in between each five-day walkout. That includes a long weekend and summer school vacation period in Britain and could also affect travelers to South Africa for the monthlong football World Cup, which kicks off on June 11.
"Regardless of the reasons behind these strikes, the people who are going to suffer the most are BA's customers," said Bob Atkinson, of travel website travelsupermarket.com. "Thousands of families will have booked their trips well in advance to and will have little flexibility, minimal realistic alternatives and will be left disappointed."
Unite said it approached BA after its members had turned down the latest offer from the airline on Friday _ following advice from angry union leaders after BA failed to restore travel perks taken away from staff who joined in strike action in March.
Union leaders are also unhappy that BA is taking disciplinary action against more than 50 union members and fired an official who represented cabin crew.
"Cabin crew are left with no choice but to take further strike action," Unite's joint general secretaries Derek Simpson and Tony Woodley said in a statement. "There can be no industrial peace without meaningful negotiations and while management victimizes trade unionists and uses disciplinary procedures in a witch-hunt."
The pair said that the required seven days' notice period gave BA time to "reopen meaningful negotiations."