https://phys.org/news/2019-03-boeing-max-safety-tragedies.html

China—an important market for Boeing—became the first country to ground the 737 MAX 8 on Monday. Ethiopian Airlines did the same, saying the decision came as an "extra safety precaution."

Only the flight data and cockpit conversation contained in the doomed aircraft's two black boxes can provide tangible evidence of what may have caused the latest accident—technical problems, pilot error or a combination of factors.