Investigations following the crashes revealed design flaws while troves of damning internal Boeing documents showed some employees expressing safety concerns, mocking regulators and boasting about getting them ease off of more stringent training requirements. The crashes and the grounding also raised scrutiny of the FAA, long the world's gold standard of aviation safety, and raising questions about whether it ceded too much power in the certification process to Boeing before it approved the planes in 2017. "We will never forget the lives lost in the two tragic accidents that led to the decision to suspend operations," Boeing's CEO, David Calhoun, said in a statement.