Days after a chunk of a Boeing 737 MAX 9 airplane flew off while the plane was in the air, a lot of questions remain unanswered. The MAX 9, the less popular of the two MAX models currently certified to carry passengers, is still grounded. The National Transportation Safety Board is still investigating. And when the planes will start returning to the air is still unknown. But in the days since the flight, residents found the fuselage piece — a plug covering a hole cut for an unused emergency door— that came loose and a passenger’s phone that survived the 16,000-foot fall. The NTSB has determine…