Additionally, the company said that it is exploring sales for its Canada and China businesses and it is looking at "strategic alternatives" for its $10 billion commercial air business.
"Over the past five years we have made significant progress in transforming CIT," Thain said in a release. "Following the completion of our OneWest Bank acquisition, we have decided to explore the strategic alternatives for our Commercial Air business and to sell our non- transportation-related businesses in Canada and China."
"These strategic initiatives will position CIT for long-term success by further simplifying our bank-centric business model as we focus on meeting the financing needs of our U.S. small business and middle market customers," he added. "We believe these decisions will increase shareholder value."
CIT said it owns and manages a fleet of more than 350 commercial aircraft that serve about 100 customers in 50 countries.
On Thain's future, CIT said its CEO's retirement will take effect on March 31, 2016, but he will continue to serve as the chairman of its board.
Ellen Alemany, a CIT board member, will join the management team as vice chairman in November, and will takeover as CEO when Thain retires, the company said.
"John has been a pivotal leader during one of the most challenging times in CIT's more than 100 year history. Under his leadership he has overseen the successful corporate and financial restructuring of CIT," Vice Admiral John Ryan, CIT lead director, said on behalf of the company's board in the release. "On behalf of the Board, employees and shareholders we extend our gratitude to John for his success and commitment to CIT."