Aon Corp. hired Gregory C. Case Monday to be president and chief executive officer.
Mr. Case was also elected to the board of directors of the big insurance brokerage. He succeeds Patrick G. Ryan, who had been Aon's CEO since the Chicago company's founding. Mr. Ryan is to be executive chairman of the board of directors. Mr. Case most recently was head of the financial services practice at McKinsey & Co., an international strategic management consulting firm.











