it s one that we want to dig into. reporter: the federal aviation administration has now grounded max 9s until airlines can make new inspections, but the incident has once again thrust boeing under the microscope. two fatal crashes grounded the 737 max for 20 months in the u.s. all right. that was pete monteen. with those details, let s talk more about this. aviation analyst myles o brian, good to see you. let s start with this missing piece, this door plug. they found it in this man s backyard in portland, oregon. the door plug, this piece that blew out, it can help investigators answer what questions? yeah. it s crucial, kate. this is one of those cases we often talk about crashes where we re looking for the cockpit voice recorder, the flight data recorder, to solve it. this is an investigation that is going to have a lot more to do