The Unite union told BBC on Sunday that emergency last-minute talks with British Airways representatives have faltered and a strike will occur as planned on Monday.
Talks between union representative Derek Simpson and British Airways chief Willie Walsh collapsed on Sunday local time, with Walsh accusing Simpson of using his Twitter during negotiations.
The union plans to strike for five days starting on Monday May 24, if the two sides are not brought back to the table.
British Airways plans to operates at 60 percent capacity on long-haul flights and at 50 percent capacity on short-haul flights in and out of London Heathrow International Airport. Service at Gatwick is not disrupted.