FACTBOX: Wall Street's turmoil at the top

NEW YORK (Reuters) - American International Group Inc replaced CEO Martin Sullivan on Sunday after the world's biggest insurer suffered two quarters of record losses from risky mortgage bets.

Sullivan exit is the latest in a series of high-profile shake-ups at companies, including Wall Street's top banks and brokerages, during a credit crisis that has led to more than $400 billion in write-downs at financial institutions globally.

* On June 15, AIG named veteran former Citigroup banker Robert Willumstad, who was already AIG chairman, as its new CEO, effective immediately.

* On June 12, Lehman Brothers Holdings Inc said it demoted Chief Financial Officer Erin Callan and Chief Operating Officer Joseph Gregory.

Chief Administrative Officer Ian Lowitt was named the new CFO and Herbert (Bart) McDade, global head of equities, was promoted to chief operating officer and president.

* On June 2, Washington Mutual Inc said it would strip Chief Executive Kerry Killinger of his title of chairman. The Seattle bank said independent director Stephen Frank would succeed Killinger as chairman on July 1.

* On June 2, Wachovia Corp said it ousted Chief Executive Ken Thompson, who had presided over a 57 percent drop in its share price over the past year.

Lanty Smith, who had replaced Thompson as chairman the previous month, was named interim chief executive. Ben Jenkins, the vice chairman and head of Wachovia's retail and business bank, was named interim chief operating officer.

* On April 23, UBS AG Chairman Marcel Ospel left the Swiss bank and was replaced by the bank's chief lawyer, Peter Kurer.