FAA considered grounding some Boeing 737 Max planes last year: source

US regulators considered grounding some Boeing 737 MAX planes last year after learning belatedly of a problem with a system that is now the main suspect in two deadly crashes, a source close to the matter said. Investigators in the Lion Air crash in October and the Ethiopia Airlines disaster in March have zeroed in on the planes' anti-stall system, the Maneuvering Characteristics Augmentation System, or MCAS. Last year, before the Lion crash, inspectors with the Federal Aviation Administration discovered that the manufacturer had de-activated a signal designed to advise the cockpit crew of a malfunctioning of the MCAS system, the source said.

from https://news.yahoo.com/faa-considered-grounding-boeing-737-max-planes-last-172113889.html