American Express says president Ed Gilligan died suddenly Friday after falling ill while flying on a corporate plane to New York.
The company says the 55-year-old executive was coming back from a business trip. It said the plane made an emergency landing.
Gilligan began working at American Express Co. 35 years ago as an intern and became president of the credit card company in 2013.
The company says he is survived by his wife and four children.
"This is deeply painful and frankly unimaginable for all of us who had the great fortune to work with Ed, and benefit from his insights, leadership and enthusiasm," American Express Chairman and CEO Kenneth Chenault said in a statement. "Our thoughts and prayers go out to his wife, Lisa, and their four children – Katie, Meaghan, Kevin and Shane. He was a proud husband and father, and his love for his family was evident in all that he did."