FILE PHOTO - U.S. Senator Richard Blumenthal (D-CT) speaks during a Senate Judiciary Committee confirmation hearing for U.S. Supreme Court nominee judge Brett Kavanaugh on Capitol Hill in Washington, U.S., September 4, 2018. REUTERS/Chris Wattie

WASHINGTON (Reuters) - Democratic U.S. Senator Richard Blumenthal on Tuesday asked American Airlines, Southwest Airlines and United Airlines to voluntarily ground all Boeing 737 MAX 8 and MAX 9 planes after two deadly crashes in recent months.

“The American aviation industry has a long history of safety and excellence, due in part to the trust passengers and their families can place in the air carriers and operators,” Blumenthal wrote in a letter to the airlines. “The common sense step now – until we have answers – is to ground these planes.”