SYB_DC
Winger
As the crash happened in Ethiopia, The NTSB don't have Primacy, The Ethiopian investigation do. Although they can relinquish it I think.
Countries have already started grounding those Aircraft so I bet they will be trying to get to the bottom of it sprightly.
NTSB will have an observer, however, as it was an American aircraft.
Not mentioned in this thread is that this is the second 737 ET has crashed this decade in the first few minutes after takeoff, and the previous one was largely attributed to crew failures. It could be an ugly dynamic here with a fairly major airline (and make no mistake, they are that - they have over 110 aircraft, roughly the same as KLM) and their biggest supplier fighting over blame for a horrible crash. Ethiopian can't really afford a conclusion that they can't safely fly 737s, and Boeing definitely can't afford a conclusion that the MAX is unsafe.