I am not normally a nervous flyer. But the similarities between the recent Ethiopian Airlines disaster and the October crash of another Boeing 737 Max 8 flown by Indonesia’s Lion Air were enough to make me applaud the decision to ground the planes while authorities figure out what went wrong.

Boeing has been working on fixes for the 737 Max’s flight control software ever since the October crash was blamed in part on an anti-stall system going awry. The software, known as MCAS, appears to have repeatedly forced the plane’s nose down because an “angle of attack” sensor misread the plane’s angle to the ground. The pilot tried repeatedly to pull the nose up but the plane fell into a fatal dive.

We are still waiting for a report on the cause of the Ethiopian crash, which killed 157 people. But on Monday, the US Federal Aviation Administration poured cold water on the company’s hopes of getting the jets back in the air quickly. “Time is needed for additional work?.?.?.?to ensure that Boeing has identified and appropriately addressed all pertinent issues,” it said.