> IIRC there was a report about a third plane that (after at least the first crash, not sure if it was before or after the second) ran into the same issue with MCAS, but correctly followed the recovery procedure and was fine. Now, it could be that the recovery procedure is unreliable, and that third cockpit crew got lucky. But I don't recall what came of all that.
> And on top of that, the two planes that crashed didn't have optional equipment (a disagree indicator, IIRC) that would have likely given the pilots extra and sufficient information to understand what was wrong and avoid a crash.
The first plane had experienced unwanted/incorrect runaway MCAS activation on the flight before the accident flight; the pilots turned off electric trim for the rest of the flight (which is part of the memory checklist) [1], and the aircraft was subsequently cleared by mechanics for the accident flight.
On the second accident flight, it seems that the pilots were unable to complete the specialized checklist for improper MCAS activation, as aerodynamic forces made manual trim impossible. Wikipedia notes that the earlier 737-200 had a procedure for recovery in this situation, but it had not been part of training for quite some time.
> And on top of that, the two planes that crashed didn't have optional equipment (a disagree indicator, IIRC) that would have likely given the pilots extra and sufficient information to understand what was wrong and avoid a crash.
I don't think knowing that the airspeed indicators disagree is enough to know what to do, in absence of knowledge of the MCAS. Perhaps, it could have helped the 2nd accident crew, if they had been able to connect the dots and disable electric trim before trim position became too extreme to manually correct. For the first airplane, I don't think it would have helped, because the implications of wrong airspeed information were unknown; maybe it would have resulted in the broken sensor being replaced after the penultimate flight though.
Sensible limits on automation would likely have prevented both accidents (and was implemented after the second accident). Transparency about MCAS may have helped with the first accident, but clearly wasn't enough for the second. Separate cutoff switches for automation and electric trim would have helped with the second flight (there's two switches already!), but knowledge of MCAS would be a prerequisite.
In the first accident, both the pilot and first officer were quite experienced, but in the second, the first officer had less than 400 hours of flight time, which is significantly less than the 1,500 hours required to be a first officer in the US. Increased flight experience may or may not have helped in this case, but is an area where US carriers differ from international carriers.
[1] https://en.wikipedia.org/wiki/Lion_Air_Flight_610#Investigat... see "previous flight problems"