. >> narrator: f.a.a. engineer joe jacobsen examined the data from the lion air crash and quickly raisedw. it was purposely designed and certified to use only one a.o.a. input to drive mcas, to move the horizontal stabilizer at a high rate. i talked to three managers, said this a design flaw. they were skeptical, not really buying in, saying the pilot should have been able to intervene. it's a failure. our job is aviation safety, and when airplanes go down we feel a, a real personal sense of loss and remorse and failure. and it affects a lot of people. ♪ ♪ >> narrator: in the fall of 2019, with the max having been grounded for seven months, congressional investigators released internal communications they found during their investigation. >> test pilots working for boeing write about problems with the mcas system two years before the first fatal crash in indonesia. >> narrator: it was further evidence of the company's attempt to avoid pilot training for the max. >> did that ever cross their minds? that they were going to let something go into the air that could pontially kill people? ♪ ♪