International Consolidated Airlines Group (ICAGY) , the parent company of British Airways, said pilots walked off the job for the first time ever Monday amid a 48-hour strike over pay that has grounded nearly all flights for Europe's third-largest airline.

The British Airline Pilots Association (BALPA) started its two-day strike earlier today after weekend talks with International Consolidated Airlines, British Airways' parent company, broke down over the weekend. Further action is also planned for September 27. The current strike is likely to affect as many as 300,000 passengers and ground around 1,600 flights, mostly from British Airway's main Heathrow hub in London.

"We understand the frustration and disruption BALPA's strike action has caused our customers. After many months of trying to resolve the pay dispute, we are extremely sorry that it has come to this," BA said in a statement. "Unfortunately, with no detail from BALPA on which pilots would strike, we had no way of predicting how many would come to work or which aircraft they are qualified to fly, so we had no option but to cancel nearly 100% of our flights."

IAG shares were marked 3% lower in the opening hour of trading in London, compared to a 0.32% gain for the broader FTSE 100 benchmark, and changing hands at 417.4 pence each.

BALPA pilots are asking for a greater share of profits from the British Airways parent, which made £2.6 billion last year. BA said its "fair and generous" 11.5% pay increase would mean some pilots would earn more than £200,000 ($245,000) per year, with BALPA countering it has "lost trust and confidence in their management through relentless cost and corner-cutting."

British Airways CEO Alex Cruz told BBC radio Monday that he was committed to "getting over this particular dispute as quickly as possible and we urge the union to sit down with us as quickly as we can so we can reach an agreement."