FILE PHOTO: A sign is seen outside a Thomas Cook shop in central London, November 26, 2014. REUTERS/Suzanne Plunkett/File Photo

LONDON (Reuters) - Pilots working for British tour operator Thomas Cook TCG.L will strike on three more days during September and October if talks starting next week fail to resolve a dispute over pay, the pilots' union said on Friday.

Thomas Cook pilots went on strike on Friday for 12 hours in what the British Airline Pilots’ Association (BALPA) said was the first walkout by British pilots in more than 40 years.

Talks, due to start on Sept. 12, have been facilitated by the Advisory, Conciliation and Arbitration Service (ACAS). Five days of negotiations will run over a two-week period.

Strikes would be staged on Sept. 23, Sept. 29 and Oct. 6 if those talks failed, BALPA said.

“There is still a significant gap between us and Thomas Cook so we cannot assume that those talks will succeed. That’s why we’ve set new strike dates,” BALPA General Secretary Brian Strutton said in a statement.

Thomas Cook said all its flights operated during Friday’s stoppage.

“We are disappointed that BALPA has announced further strike dates. We have set out a fair pay increase,” a Thomas Cook spokesman said in a statement, urging BALPA to negotiate.

“BALPA have not moved from their demands for a pay rise which adds up to more than 10 per cent, or around 10,000 pounds ($13,217.00) per pilot,” it said.

(This story changes paragraph 4 after BALPA corrected the October strike date)