The ongoing Boeing quality control issues, after the Alaska Airlines 737 MAX 9 door accident, are raising red flags at one the world’s leading aviation analysts.

New York-based Berstein in its report “Boeing, Spirit Aerosystems: MAX-9 incident - Where we stand now? What are the big questions?” raises timeline doubts about the certification of other Boeing models such as the 737 MAX 7 and 10 and the long-delayed 777X as a result of the inspections of the MAX 9 exit plug doors.

Those inspections by Alaska and United have revealed loose bolts and other issues with the door plug (below).

Bernstein says that the issue of Boeing quality issues is now that there is “a pattern of poor workmanship that led to quality escapes.” It adds that it “believes that these most likely originated at Spirit Aerosystems”, where the fuselage is assembled. But, Boeing could potentially have had a role or at least should have had better inspections or oversight at Spirit.”

Bernstein says that it does not believe this is a “737MAX problem” or design issue “as the door plug on the earlier 737-900ER is virtually identical and those airplanes have flown millions of hours with no known incidents like this.”

Berstein says that “if Spirit is where this originated, this increases the scope of issues that new CEO Pat Shanahan needs to address as he works to restructure operations in Wichita.” Mr Shanahan, when at Boeing, turned the 787 production fiasco around.

Berstein believes the impact of this specific problem [MAX 9 door plug] is relatively small - but, warns “That is not what is most important. Where the impact could be large is the concern of “how do we know there are not even more problems like this?”.

It warns that “heightened FAA scrutiny could also delay certification of the 737MAX-7, 737MAX-10, and 777X.

Bernstein says that ultimately, it expects few customers will switch away from the MAX. “Fleets and even sub-fleets at large carriers need commonality. Operators have appeared happy with the MAX and there are few A320s available in any case.”

Bernstein says Boeing has serious questions to answer.

“Boeing has had a substantial number of quality problems extending back several years. Those have included defects related to Spirit, such as the 737MAX tail fittings and aft pressure bulkhead holes. But, others have been more directly with Boeing, such as a recent loose rudder bolt and nonconformities on 787 composite structures,” warns Bernstein.

It adds “Even if one can trace the problem to Spirit, for example, at the end of the day it is Boeing’s responsibility to inspect and deliver a safe airplane.”

“After many quality issues, the question that continues to arise (both directly to us and in the media) is“how do we know there is not a next problem that could happen any time?”.

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Berstein says it believes “that is a legitimate question and the most important one for Boeing right now.”

It adds “Boeing management has stressed the importance of quality control and safety since the beginning of the MAX grounding. This event and the multiple airplanes that appear to have quality escapes raises questions about the processes in place and certainly requires more explanation on how this situation came about.”

On an upbeat note Bernstein says that barring any further issues, it does not expect to see customers move away from the 737MAX or Boeing more broadly. “Since the MAX has been ungrounded, we have heard positive feedback on the MAX in terms of performance. The biggest complaint has been about not getting the airplanes quickly enough.”