The British Airways cabin crew union, Unite, has announced fresh strike dates in its long-running dispute with the airline.
Cabin crew will walk out for four separate five-day strikes in May and June.
The first strike will begin on 18 May, ending on 22 May, with the three further strikes beginning on 24 May, 30 May and 5 June.
Unite members rejected a fresh deal for cabin crew earlier this month.
The union said there was a turnout of 71% of the cabin crew it represents, and 81% voted against BA's offer last week, which sought to resolve the dispute over pay and working conditions.
Details of that deal were not given, but Unite said BA had failed to restore the travel perks it withdrew from staff involved in the previous strikes in March.
Those stoppages grounded hundreds of flights and cost BA an estimated £45m.
The newly-announced strikes will see staff walk out for a total of 20 days, covering spring bank holiday and school half-term holidays.
Football fans planning to fly out to the World Cup in South Africa could also be affected, with the last of the five-day stoppages beginning on the weekend before the tournament starts.
However England's first game against the United States kicks off on 12 June, after the final strike has ended.
In a statement, Unite's joint general secretaries Derek Simpson and Tony Woodley blamed BA for forcing cabin crew to again resort to industrial action.
"There can be no industrial peace without meaningful negotiations and while management victimises trade unionists and uses disciplinary procedures in a witch-hunt," they said, claiming that a Unite approach made over the weekend had been rejected.
"The seven days' notice period is sufficient time for BA management to do the sensible thing and reopen meaningful negotiations," they added.
BA defended its approach to the latest negotiations.
"We have made a very fair offer, which meets the concerns the union raised during 14 months of negotiations and also ensures that our crew remain the best rewarded in the UK. That offer remains available," BA said in a statement.
The airline condemned the decision to strike, saying it showed "a callous disregard" for BA customers and staff, but added that it was already planning contingency measures to ensure as many passengers as possible fly during the strike periods.
All flights from Gatwick and London City airports are expected to operate as normal, BA said, while a "substantial" number of long-haul flights from Heathrow will run as planned.
There will be daily flights from Heathrow to all short-haul destinations, BA said, but did not give any numbers.
As with the strikes in March, the airline is also planning to lease extra aircraft from other carriers and re-book passengers on cancelled flights onto other airlines.