Boeing Co.’s 737 Max jet was supposed to be the safest plane in the world. The perception is anything but.

Almost five years after the second fatal crash involving the plane prompted a global grounding, and three years after the Federal Aviation Administration said the Max could safely return to US skies, the aircraft is still having troubling safety problems. Alaska Air Group Inc. grounded its entire fleet of Boeing 737 Max-9 aircraft after a piece of the plane blew off soon after takeoff on a late Friday evening flight, leaving a gaping hole with views of the starry night where a panel should have been.