WASHINGTON – United Airlines and Chicago airport officials missed a deadline for answering questions from by key U.S. senators about the dragging incident aboard a United Express plane.

The company and city say they want more time.

Four leaders of the Senate Commerce said Friday it was unacceptable that the airline and city had not answered questions about the April 9 incident. Their deadline passed Thursday.

In a letter to the senators, CEO Oscar Munoz said United Continental Holdings Inc. needed until April 27 to thoroughly investigate the matter and review policies including how it handles “oversold situations.” He apologized again for the “shameful treatment of one of our passengers.”

Chicago aviation commissioner Ginger Evans asked to have until April 26 to answer questions.

The top two Republicans and top two Democrats on the Senate committee asked United about its policy for bumping passengers off overcrowded flights, and whether the airline handled cases differently once passengers had boarded.

Passengers had already boarded the United Express plane when the airline, needing to find seats for four crew members, called airport security officers to help remove a 69-year-old passenger. He was yanked out of his seat and dragged down the aisle.