"It is completely unacceptable that BALPA is destroying the travel plans of tens of thousands of our customers with this unjustifiable strike action", said BA in a statement when the strikes were first announced.
"We are extremely sorry that after many months of negotiations, based on a very fair offer, Balpa has decided on this reckless course of action".
The carrier, which is owned by London-listed International Airlines Group, said it has cancelled almost 100% of its 850 daily flights, affecting the travel plans of more than 100,000 passengers.
Empty check-in desks stand in Terminal 5 at London Heathrow Airport in London U.K. on Monday Sept. 9 2019. Simon Dawson Bloomberg
British Airways pilots kicked off the first day of their two-day strike on Monday, sending over 1,500 flights into cancelation and around £80M or $98M in lost revenue.
"It's going to punish customers, it's going to punish our brand, it's going to punish the rest of the colleagues", BA Chief Executive Alex Cruz told BBC TV as IAG shares dropped by as much as 3 per cent in early trading.
Pilots would also like a better profit share-scheme that other major airlines offer, as well as a company share-scheme that most major United Kingdom companies offer to employees.
The airline told CBS News it could not give a specific breakdown on how many flights to and from the USA would be affected, but confirmed that virtually all of its total daily flights, a number usually around 850, were canceled.More news: Government Will Respond To Demand Of Auto Industry
British Airways says it has offered pilots an 11.5% pay raise over three years but the union says its members want a bigger share of the company's profits.
The disruption hit hardest in London, where BA operates from its twin hubs at Heathrow and Gatwick.
Heathrow's Terminal 5 is virtually empty of passengers during the British Airways pilots' strike.
Pilots were also told that they will see one of the most popular travel perks that BA boasts of. It also says that flights on BA CityFlyer, SUN-AIR and Comair are not affected by the strike.More news: Meghan Markle ranked as number one social climber in the UK
"Airlines will often reject passengers' claims for compensation by arguing that strikes are beyond the airline's control and that airlines are thus not responsible for paying for compensation", according to AirHelp, but "a flight disruption caused by airline staff strike is definitely eligible despite what the airline states". "However, it is a definite inconvenience to passengers who have been impacted, particularly for those who had urgent business and could not postpone their travel", said Sharat Dhall of Yatra.com.
"Pilots are standing firm", Balpa's general secretary Brian Strutton said in a statement. Further strikes are planned for September 27.
The current demands relate to pay, profit sharing, and a share-awards program, and come after cockpit crew took salary cuts in the wake of the financial crisis to help bolster the airline's finances, according to the union.
Both BA and the pilots' union Balpa has indicated that they are willing to start new talks. IAG's stock has fallen more than 31% this year, partly in expectation that the dispute with pilots would culminate in a strike, Berenberg's Yanoshik said.More news: Britain will leave the European Union on time, PM Johnson's adviser Cummings says
Pilots vowed to strike following a breakdown in talks over a new contract.