British Airways is facing the danger of more strikes over the summer after union leaders said they would ballot cabin crew members for additional action in a bitter dispute over changes to pay and working conditions.

As the last of 22 days of walkouts - which since mid-March have price the airline more than 150 million pounds ($220 million) - drew to a close on Wednesday, there was small sign of a resolution to the dispute, with BA boss Willie Walsh vowing to hold out as extended as it takes.

Though BA has been forced to cancel hundreds of flights because of the walkouts in March, May and June, it has gradually increased services during the strike period as less workers participated in the action and it used quickly-trained staff from other departments.

The airline has also used leased planes and crew and booked its passengers onto flights with contestant airlines in a bid to minimize the disruption, allowing it to operate around 80 percent of its long-haul flights from Heathrow in the very last five-day walkout.