The first strike is scheduled to take place over three days from March 20 to March 22, followed by a second four-day strike from March 27 to March 30.
The airline said it aimed to fly around 45,000 passengers each day during the first strike, using volunteer cabin crew and 22 hired aircraft. The rest, around 30,000 passengers, will be put on other airlines, or offered seats on alternative BA flights.
BA will operate all longhaul flights and more than half its shorthaul flights from Gatwick. All flights in and out of London City airport will be unaffected by the strike action.
BA chief executive Willie Walsh said the flag-carrier will operate a significant proportion of services during the first phase of the strike. He apologised to customers, calling the planned strikes a "cynical attack" by Unite, the union representing cabin crew.
Unite called for the strikes following breakdown of talks with BA over cutting costs. A new BA proposal was due to be put to Unite members but was withdrawn following the announcement of strike dates.
The union has offered to suspend the strikes if BA resubmits the offer. BA on the other hand has accused Unite's joint general secretary Tony Woodley of a "cynical manoeuvre", insisting the offer had been rejected by Unite negotiators when it was tabled last week.
The company's unilateral decision to axe over 1,100 cabin crew posts since November sparked the dispute with the union.
BA has already offered full refunds to anyone booked to travel between 19 and 31 March. It has also opened an extra call centre manned by volunteers to help customers with rebooking and refunding queries.
