Some discussions and media articles risk confusing complementary but different processes in certification.
Aircraft certification - CS 25 requirements, essentially relates to design aspects, but including crew activities (HF).
Flight Standards reviews are more focussed on operational implementation, guided by Ops requirements (121) and Advisory materials; this includes the level / extent of training and judgement of same type rating.
Aircraft type certification is initiated and led by the host nation (Boeing / FAA); other certification authorities can validate / accept the basis of certification Part 25 ~ CS 25, add special requirements, or apply specific interpretations.
Operational approval is less well defined; the lead authority’s position can be used as a basis, but more often reinterpreted and adjusted by others to meet national requirements.
Thus aircraft certification by the lead authority is widely agreed, but operational approval less so.
In this instance, the certification aspect of the MCAS modifications have to meet FAA Part 25; each national authority considers acceptance, validation, or applies special conditions. It would be surprising if there was not an agreed positon, even if not as the initial Boeing / FAA proposal (normally closed doors meetings).
The FAA Flight Standards (re) review, could agree that their initial position is still valid after modification; i.e. the intention and effect of MCAS is unchanged even though its initial mechanisation and notification were flawed (Fight Ops didn’t know) - a public view, link below.
A weakness in this process is that local viewpoints (operators) can sway operational decisions, such that there could be significant differences with other authorities who represent more worldly views. In this instance the latter is very important due to the nature and location of the accidents (Boeing / FAA should build and certificate aircraft for the world; not just local operators).
Having an independent international group consider ’certification’ issues is very unusual, even more so with ex NTSB chairmanship. Its task is reported as “…
evaluate the automated flight control design and determine whether it complies with regulations. It also will decide if changes need to be made in the FAA’s approval process.” (90 days!)
It would be surprising if ‘aircraft certification’ (part 25) of MCAS modification were to be reviewed; this would question the FAAs fundamental right (ability) for approval (a US issue not international). Thus probably not an international public review of the failings in certification (Boeing / FAA); but a US investigation is still required.
However, a wider review of technical certification aspects based on what has been learnt from the accidents would be most valuable, even if not helpful to Boeing /FAA. Link to discussions below.
More likely the task is to agree a common operational view, or sufficiently similar so that the FAA is not isolated, and restores credibility. The timescales for this might not restrict a return to operations, even though some authorities could differ from the FAAs position.
Some of the technical issues, overlapping both certification and operational aspects are discussed in #696
Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed and #703
https://www.faa.gov/aircraft/draft_d...ev17_draft.pdf
FAA update
https://www.faa.gov/news/updates/?newsId=93206