> there is some certification requirement that the pitch has to be constant during climb (or something like this); if the plane doesn't have this, it is not certified to fly. It wouldn't pass FAA certification without MCAS.

So what I gather is the issue was that the MAX didn't fit this requirement for steady pitch (hence the airframe problem referenced in the linked article), and MCAS was supposed to be the band-aid to fix this essentially by automatically pushing forward on the yoke during high angle of attack.

If that's the case then the following is especially concerning:

> Boeing offered the single angle-of-attack sensor as standard equipment, and charged extra for a second along with a “disagree” indicator that would allow 737 MAX pilots to “cross-check” a faulty sensor.

Seems pretty sketchy to ask airlines to cough up extra dough for redundancy on a safety critical system. Who knows what other systems are subject to the same cost/benefit tradeoffs.