When you compare AS9100D with AS9100C the first thing you'll notice is
that the structure has changed. The old standard had five main sections
(4 to 8) while the new one now has seven (4 to 10). This is because the
underlying ISO 9001 2015 standard uses the new Annex SL template.
According to ISO, all future management system standards (MSSs)
will use this new layout and share the same general requirements.
As a result, all new MSSs will have the same basic look and feel.

A common structure is possible because concepts such as management,
customer, requirements, policy, procedure, planning, performance, objective,
control, monitoring, measurement, auditing, decision making, corrective action,
and nonconformity are common to all management system standards. While this
will make it easier for organizations to implement multiple standards because they
will all share the same basic requirements, it may cause some disruption in the
short run as organizations get used to the new structure.

When you look more closely, you’ll also notice that AS9100D simply copied
most of the old AS9100C text, edited some of it, and then pasted it into the
new seven part structure wherever it seemed to fit. It also removed some
items and added a few new clauses as well.

But perhaps the most important changes include the removal of preventive
action, a greater emphasis on product safety, and an entirely new focus
on human factors and counterfeit parts.

Despite the fact that most aviation, space, and defense organizations depend
on preventive action in their day-to-day operations, AS9100D has decided to go
along with ISO's odd decision to abandon preventive action and replace it with
an entirely new concept: “risk-based-thinking” (discussed below). Of course,
this doesn't mean that you have to toss it out as well. You're certainly free
to continue taking preventive action whenever necessary.

While the previous change might be the most surprising one, the decision to
expand the section on product safety is not entirely unexpected. While AS9100C
briefly discussed product safety in two sections (7.3.1 and 7.5.5) and mentioned
it in two notes (7.1 and 8.1), it now has its own definition (3.4), its own section
(8.1.3), and is discussed in three other sections (7.3, 8.1, and 8.4.3). AS9100D
(8.1.3) now expects you to “… plan, implement, and control the processes
needed to assure product safety during the entire product life cycle ….”

In addition to the previous rather significant changes, AS9100D section
10.2.1 now also expects you to consider “human factors” when analyzing
nonconformities, identifying causes, and developing corrective actions.
It now expects you to determine “the causes of ... nonconformity,
including ... those related to human factors”.

This simply acknowledges the obvious: when people perform tasks they are
affected by things like fatigue, stress, and morale. It simply acknowledges the
fact that workers are influenced by how much knowledge they have, how well
they communicate, how much pressure they feel, and how much personal
support and encouragement they receive from coworkers and managers.

While the previous changes are certainly interesting and important, the new
focus on the prevention and control of counterfeit parts may well be the most
far-reaching and have the most impact. AS9100 now expects you and your
suppliers to prevent the use of counterfeit parts and if this fails to make
sure that they don't reenter the supply chain.

AS9100D section 8.1.4 wants you to “... plan, implement, and control
processes … for the prevention of counterfeit or suspect counterfeit part
use and their inclusion in products delivered to the customer.” Section 8.4.2
goes on to say that “Verification activities of externally provided … products
shall be performed when there is high risk of counterfeit parts” and sections
8.4.3 and 8.7.1 go even further. Section 8.4.3 now expects you to tell your
“external providers” to also “prevent the use of counterfeit parts” and
section 8.7.1 says that the counterfeit parts that have been identified
“shall be controlled to prevent reentry into the supply chain."

Also see ISO 9001 2015 versus ISO 9001 2008