WASHINGTON (Reuters) – U.S. Senate Commerce Committee chair Maria Cantwell on Thursday asked Southwest Airlines to provide a full accounting of all refunds issued and denied after a December technological meltdown led to the cancellation of 16,700 flights.

Cantwell asked Southwest Airlines Chief Operating Officer Andrew Watterson for detailed data from the travel disruptions. Watterson said last week the airline had paid hundreds of millions of dollars in compensation and reimbursements for traveler expenses.

(Reporting by David Shepardson)