London, England (CNN) -- Saying it plans to lease aircraft and provide replacement workers, British Airways on Monday unveiled an ambitious contingency plan in preparation for the first of two strikes by the union members representing the airline's cabin crews.
The Unite union's leadership aimed to ground the airline through its action, but "the flag will continue to fly," said Willie Walsh, BA chief executive, in a written statement.
"Around 60 percent of our customers will be able to fly as planned and many thousands more can be rebooked onto alternative BA flights or onto rival airlines."
Members of the Unite union voted to strike for three days beginning March 20, and for four more days beginning March 27.
BA said Monday its contingency plans will allow about 45,000 customers to fly each day during the first strike period.
"At this stage, the vast majority of flights between March 23 and March 31 remain in the schedule, and we will update customers due to fly during the second strike period after the first strike period has ended," the statement said.
"The airline is still available to hold further talks but wants customers to have early warning of its flying schedule to allow sufficient time for alternative travel arrangements to be made."
At London's Heathrow Airport, more than 60 percent of British Airways long-haul flights will be operated during the first strike period, the company said. In addition, it will operate all long-haul flights to London's Gatwick Airport and more than half of the short-haul flights at Gatwick.
"The airline will operate some of its own short-haul flights at Heathrow, and will supplement its schedule by leasing up to 22 aircraft with pilots and crews from eight different airlines based in the UK and Europe," the statement said.
"Due to the numbers of cabin crew who have called in to offer their services over the weekend, the schedule will be slightly larger than we had originally anticipated," Walsh said.
The airline said it has also made agreements with 40 other carriers to rebook customers free of charge during the strike period if their British Airways flights are canceled.
"We will continue to try to prevent this strike taking place, but we have reached a point when we must now offer some clarity to our customers who have waited with great patience since Friday, when the strike dates were first announced," Walsh said in the British Airways statement.
"... I recognize the frustration of customers booked for travel from March 27 onwards, when the second stoppage is due to begin, and we will do all we can to give them more clarity about their specific flight number once we start to understand just how many cabin crew are willing to work as normal."
The industrial action is over planned changes to cabin crew conditions, which British Airways says will save the carrier more than £60 million (approximately $90 million) a year. Unite has said the plans call for working hours to be extended and crew levels to be cut, changes that it has said will damage customer service and the BA brand.
The airline's management submitted a formal offer to the union Thursday, Unite said, but added that the offer failed to address union concerns about crew numbers and service delivery. That prompted Unite officials to announce the strike dates Friday. When that occurred, the airline took its offer off the table.
The airline, for its part, also has rejected all union proposals so far, saying they would have saved the airline significantly less money than the airline's own planned changes.
British Airways has opened an extra call center manned by volunteers to help customers, the Monday statement said.
"We remain absolutely determined to search for a sensible settlement and our door remains open to Unite, day or night. It is not too late for ... Unite to call off this action and we will do all we can to reinstate some of the canceled flights," Walsh said in the company's statement Monday.