British Airways, which is slashing thousands of jobs as coronavirus decimates the travel sector, said Monday that CEO Alex Cruz is stepping down "with immediate effect" but gave no reason.
Parent group IAG added in a statement that Cruz, who has been BA chief executive for four and half years, will be replaced by its Aer Lingus boss Sean Doyle but will remain non-executive chairman.
A company spokeswoman declined to comment on media speculation over the nature of his departure.
British Airways is currently in the process of axing 13,000 jobs or about one third of its workforce in response to the fallout from the Covid-19 pandemic, which has decimated demand for air travel.
New IAG chief executive Luis Gallego, who took the reins from Willie Walsh just last month, said Monday's reshuffle was aimed at emerging stronger from the health crisis.
"We're navigating the worst crisis faced in our industry and I'm confident these internal promotions will ensure IAG is well placed to emerge in a strong position," Gallego said in the statement.
"I want to thank Alex for all that he has done at British Airways. He worked tirelessly to modernise the airline in the years leading up to the celebration of its 100th anniversary.
"Since then, he has led the airline through a particularly demanding period and has secured restructuring agreements with the vast majority of employees."
Cruz gave no comment on his surprise departure.
Speaking last month, he defended heavy job cuts at the airline and argued that customers were "still afraid of travelling".
"Covid has devastated our business, our sector. We're still fighting for our own survival," he told parliament's transport select committee.
IAG has forecast that it will take until at least 2023 for passenger demand to recover to pre-pandemic levels.
BA pilots voted in July to accept a package including job and pay cuts aimed at avoiding even more redundancies.
Cruz told lawmakers that the pandemic had created an "impossible situation".
"As CEO of British Airways, I have to take responsibility. I cannot ignore the situation. I had to act incredibly fast," Cruz said during his parliamentary grilling on September 16.
"I deeply, deeply regret that way too many loyal and hardworking colleagues of mine are having to leave our business and I understand why MPs are concerned."
He added: "This is an impossible situation. I am completely dedicated and focused on protecting those nearly 30,000 jobs of all those BA colleagues who will remain within the business.
"People are still afraid of travelling... We don't see a short term coming-back of our passengers."