Those are the findings of a multiagency task force due to release its findings Friday, according to a report in The New York Times.
"The JATR team found that the MCAS was not evaluated as a complete and integrated function in the certification documents that were submitted to the FAA", the 69-page report said.
American Airlines said on Wednesday it expects its fleet of Boeing 737 Max jets to return to passenger service later than expected on January 16, 2019, after the Federal Aviation Administration (FAA) and Department of Transportation (DOT) sign off on revisions meant to remedy flaws that led to the deaths of 346 people in two crashes. Many critics say the FAA should take a bigger role.
A report Friday by worldwide aviation regulators criticized the US Federal Aviation Administration's certification of the MAX.More news: Advance Polling Stations open Friday
FAA Administrator Steve Dickson has said he will review every recommendation made in the "unvarnished" review.
In both of the crashes, a single damaged sensor plunged the plane into a irremediable nose dive just minutes after take-off, leaving pilots with no chance of correcting the 737 MAX's path.
Boeing has not yet responded to a DailyMail.com request for comment.
"With adequate FAA engagement and oversight, the extent of delegation does not in itself compromise safety", the report said.More news: Why Jennifer Aniston Returned to Television With Apple’s ‘The Morning Show’
The Joint Authorities Technical Review, released Friday, finds Boeing failed to explain thoroughly how much the MCAS system - the anti-stall software at the heart of two deadly crashes - had been changed from previous plane models.
Boeing pledged to work with the FAA on the recommendations.
The review also found "signs of undue pressure" on Boeing employees performing tasks for the FAA, "which may be attributed to conflicting priorities and an environment that does not support FAA requirements".
The aviation panel report also said the FAA must ensure manufacturers "provide a full list of all aircraft proposed changes (no matter how trivial)".More news: Former Ukraine envoy scheduled to testify in Trump impeachment probe
"Boeing is committed to working with the FAA in reviewing the recommendations and helping to continuously improve the process and approach used to validate and certify airplanes going forward", the company said in a prepared statement. European Union Aviation Safety Agency (EASA) officials told senior US counterparts that one element of the fixes, having two flight control computers operate simultaneously, goes against decades of prior design and has not been adequately tested, the news agency wrote.