Delta Air Lines announced Wednesday that Richard Anderson, who started as CEO in 2007, will retire May 2 to become the executive chairman for the carrier's board of directors. In his stead, Ed Bastian, Delta's current president, will become CEO, while Glen Hausenstein, Delta's current vice president, will become president.

"Today I announced my retirement as CEO of Delta after nine years of service to this great company," Anderson wrote in a letter to employees, according to Business Insider. "Thank you for the opportunity to serve you, our customers and our shareholders."

"Take care of each other and this great Company," he wrote in closing. "More than anything else, I will miss all of you."

Anderson assumed control of Delta in 2007, just after Delta exited bankruptcy protection. He oversaw a merger with Northwest Airlines that closed in 2008. Many questioned the logistics of combining the two, but it went through without any hitches. The success of this merger is often cited as the standard for most other modern airline mergers, some of which didn't pan out as well.

Following the merger, Delta became the No. 1 airline globally by market value, outpacing its U.S. rivals in terms of on-time performance and customer satisfaction. The airline has since grown in top business markets like New York, and acquired stakes in other airlines abroad, such as the United Kingdom and China.

"Sometimes being a contrarian is a good thing," said Bastian in a post on Delta's news website in November, according to Reuters.

One of Anderson's most notable actions was the purchase of a refinery in 2012 in a bid to manage fuel costs - a first for any in the airline industry. Despite initial losses, the refinery proved to be a profitable venture for the airline, posting gains of more than $300 million in 2015.

Last year, Delta reported annual adjusted, pretax profits of $5.9 billion, and recently surpassed United to become the United States' No.2 carrier in terms of revenue passenger miles. It lags only behind American, which became the largest carrier following its merger with US Airways last year.