By Siddharth Philip | Bloomberg

British Airways grounded most of its flights for the next two days as it faces its first strike by pilots in decades, a walkout that could cost the carrier 80 million pounds ($98 million).

The airline canceled "the vast majority” of its 850 daily, round-trip flights, a spokeswoman said Sunday, after the weekend yielded little progress toward a resolution of the pay dispute. Industrial action is also planned for Sept. 27, a statement on BA’s website said.

The disruptions will affect mainly London, where BA operates from its hub at Heathrow airport and also Gatwick. The outages will also extend to other locales such as Edinburgh, though London City, popular with business travelers, won’t be affected as those flights are operated by BA’s CityFlyer affiliate.

The strike would be the company’s first involving pilots since the 1970s and could cause travel chaos for customers at the tail end of the busy summer season. Passengers that are affected have been rebooked with other airlines or given alternate dates to fly, the BA spokeswoman said. Others have been given refunds.

Pilots vowed to go-ahead with the strike following a breakdown in talks over a new contract. The airline has accused the British Airline Pilots’ Association union of not acting in good faith by making "an eleventh hour inflated proposal” which BA said would cost an additional 50 million pounds. The pilots say that BA has ignored reasonable proposals for higher wages and improved benefits and their demands amount to a fraction of that sum.

The pilots have "consistently offered up chances for the company to negotiate a way forward,” Brian Strutton, general secretary of the pilots’ union, said in an emailed statement on Sunday. "British Airways must now put the needs of its staff and passengers first and accept that its pilots will not be bullied or fobbed off.”

The airline has sent an email warning the pilots that anyone who goes on strike will lose generous travel perks for themselves and their families for the next three years, the FT reported. BA has issued "various threats which suggest BA has no intention of helping defuse the situation,” the pilots said in their statement

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.

IAG SA, BA’s parent company, reported an 18% jump in profit in first quarter led by earnings at the carrier, the best performance by an airline in the June quarter. A strike would be the biggest threat to sustaining that growth, with the carrier saying the disruption could cost 40 million pounds a day. The pilots union put the cost of settling the strike at 5 million pounds, "one eighth of the cost of just one day’s strike action,” the statement said. IAG’s shares have fallen 30% in London this year.

The union called for the action after mediated talks with management at the state-backed Advisory, Conciliation and Arbitration Service ended without a deal. Cockpit crews voted to strike by a 93% majority in a poll in July.

Balpa is also campaigning at Ryanair Holdings Plc, where U.K. pilots plan to walk out for an additional seven days. Five days of strikes failed to disrupt schedules or bring the discounter -- which uses many non-unionized pilots on contract -- back to the bargaining table.