Comment by error503

Yes, this was the root of the miscommunication. The AoA indicator (ie. an instrument that gives a numeric value of AoA to the pilots) was optional. The AoA disagree alert (ie. an indication that the two AoA sensors do not agree) was not intended to be optional, and I believe it's required equipment, but it ended up tied to the indicator option. What is worth noting about this is that Boeing knew about it for a long time (I forget the timeline, but at least a year, I believe), without telling airlines or releasing a fix.

I'm not sure where the NYT information comes form that AOA DISAGREE was an option. The congressional report https://democrats-transportation.house.gov/imo/media/doc/202... is pretty clear on this aspect:

> Boeing has publicly blamed its software supplier, a company now known as Collins Aerospace Systems, for tying the AOA Disagree alert, which was supposed to be a standard feature on all 737 MAX aircraft, to an optional AOA Indicator display714—the result of which rendered the AOA Disagree alert inoperable on more than 80 percent of the MAX aircraft.