WASHINGTON, March 21 (Reuters) - The CEOs of American Airlines, United Airlines, Visa and Mastercard will not testify at an April 9 hearing on credit card competition, the chair of the Senate Judiciary Committee said Thursday.

Senator Dick Durbin in February invited the executives of the firms that have fought his legislation seeking to reduce fees charged by Visa and Mastercard on transactions. "They're just too darned busy to come and explain the major source of profits for their businesses," Durbin said. (Reporting by David Shepardson)