Richard Anderson is chief executive officer of Delta. 051012andersoned

MIAMI — Richard Anderson, the Delta Air Lines CEO whose bold moves have reshaped the airline industry, and transformed the Atlanta-based carrier into one of the most successful and most consistently profitable U.S. carriers, has retired today as the airline’s executive chairman, effective immediately.

The move came as a surprise, given the short time Anderson spent as board chair. While he had been a board member since April 2007, he did not become chairman until last May, when Ed Bastian succeeded him as CEO. The carrier has declined to explain the reasons behind Anderson’s abrupt retirement.

Francis S. “Frank” Blake, who has been lead director since May 2016, will succeed Anderson as Delta’s non-executive chairman. Blake, the former Chairman and CEO of The Home Depot, joined Delta’s board in July 2014.

“Under Richard’s leadership, Delta people established themselves as leaders in reliability, customer service and financial performance,” Blake said. “His years of service to Delta established a legacy of unmatched dedication to our customers, employees, investors and the communities we serve. He is one of the great leaders in global aviation, and we wish him well.” Blake said in a statement.

Considered the mastermind behind the merger between Northwest Airlines and Delta, Anderson opened the path to a massive consolidation in the U.S. airline industry—and to an unusual period of high profits. In July 2015, Delta took a 3.6 percent of China Eastern Airlines Corp, and later in September of that year, Delta threefolded its stake in Brazilian carrier GOL, and back in 2012, agreed to buy 49 percent of Virgin Atlantic Airways, establishing a joint-venture.

Also, he became one of the leading voices behind a heated dispute between U.S. legacy carriers (Delta, American and United) and Gulf carriers (Emirates, Etihad and Qatar Airways), which Anderson accused to have benefited from government subsidies, allowing them to move into the US market under existing US / Middle East open skies agreements.