The president of American Express Co., who was viewed as a likely successor to Chief Executive Kenneth Chenault, collapsed and died on the way home from a business trip Friday. His death sent shock waves through the New York company where he had worked since he was a college student.

Edward Gilligan, 55 years old, was traveling on a corporate plane returning to New York from a trip to Japan when he fell ill, the company said. Other executives also were on the plane, a spokesman said.

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