None of the commercial airline industry pilots — of course the test pilots employed by Boeing knew.
“We’re p*ss*d that Boeing didn’t tell the companies and the pilots didn’t get notice obviously, as well,” president of Southwest Airlines’ pilot union Capt. Jon Weaks said to the Wall Street Journal. “But what we need now is… to make sure there is nothing else Boeing has not told the companies or the pilots.”
I started up power plants for a living and never once did we even THINK about telling the operators we were training that "you don't need to know about this system because we don't think you will ever operate the plant in a way that this system will ever take over."
"Boeing said...that the stall-prevention system is not mentioned to pilots in the aircraft flight manual because it didn’t think pilots would fly the plane in such a way that the automatic system would ever take over..." Pilots for American Airlines and Southwest were told MCAS was installed “to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall.” Southwest also told its MAX pilots that in theory, they would never see the system kick in. "Since it operates in situations where the aircraft is under relatively high g load and near stall, a pilot should never see the operation of MCAS."