The strike was imposed by the British Airlines Pilot Association (BALPA) amid a heated dispute over payment with the airline.
BALPA stated on Twitter on Sunday
that it had submitted a proposal to the carrier's management on Wednesday but had not yet received a response.
British Airways said in a statement issued on Monday that it remains "ready and ready to return to BALPA negotiations".
The airline said it had to cancel so many flights because "without the details of BALPA on which pilots would strike, we could not predict how many would come to work or which planes were qualified to fly."
Customers who have booked flights on Monday and Tuesday are likely "unable to plan," British Airways said. The airline also advised customers not to go to the airport.
The members of the pilot union voted 93% for the strike in July. BALPA said last week it would like to end it if British Airways returned to the negotiating table.
According to its website, BALPA represents over 1
0,000 pilots in the UK – more than 85% of all commercial pilots flying there.
The pilot union also intends to strike on 27 September. British Airways said on Monday it would contact "in the next few weeks" to let customers traveling on or around this date know if they were affected.
While calling for higher wages, the British Airways said it was proposing an 11.5% increase over three years "fairly" and above the current inflation rate of the United Kingdom. A statement released last month said the strike could "destroy the travel plans of tens of thousands of our customers." He called the strike "a reckless course of action."