People hold photos of Boeing 737 plane crash victims as Stephen Dickson, chief of the Federal Aviation Administration (FAA), testifies before the House Committee on Transportation and Infrastructure during a hearing on "The Boeing 737 MAX: Examining the Federal Aviation Administration's Oversight of the Aircraft's Certification" in Washington D.C., the United States, on Dec. 11, 2019. Steve Dickson said Wednesday that aviation regulators won't likely clear Boeing's troubled 737 Max airplanes for flight until 2020. (Photo by Sarah Silbiger/Xinhua)