More than 1,500 flights have been cancelled as the company was accused of bullying its own staff by union bosses, who warned they could continue the action until the end of the year, The Telegraph reported.
Some 280,000 people will be affected by the strike which is set to continue on Tuesday, costing BA 80 million pounds ($98 million) in lost revenue.
Flights to New York, Delhi, Hong Kong and Johannesburg have all been affected, with the airline telling passengers: "If your flight is cancelled, please do not go to the airport."
Travellers have been offered full refunds, flights on different carriers, or the option to fly on a different date, but should not turn up at the airport without a confirmed flight.
BA and The British Airline Pilots' Association (BALPA) are clashing after the union rejected a proposed 11.5 per cent pay rise for its pilots, taking their pay package to around 200,000 pounds a year.
BALPA says that BA "has resorted to breaking agreements and threatening pilots who will strike, which is bound to make matters worse" after they emailed their 4,300 pilots on Friday warning that strike action would be a 'serious breach' of their contract.
The airline further threatened to withdraw a travel perk, where staff can book tickets for ten per cent of the full fare plus taxes, for three years if they chose to strike.
BALPA branded the airline's behaviour "illogical and irresponsible" and "will further deepen the fall out with their pilots", reports The Telegraph.
British Airways said on Sunday: "We're extremely sorry for the problems caused by the strike action called by the pilots' union, BALPA on 9, 10 and 27 September.
"We continue to be available for constructive talks with BALPA, on the basis that there are no pre-conditions to those talks.
"If you have a flight booked with us on those dates, it is likely that you will not be able to travel as planned due to BALPA's strike action. We are offering all affected customers full refunds or the option to re-book to another date of travel or alternative airline."
( With inputs from IANS )