Is it where the accident occurred or where the manufacturer is located?

Yes

Is the proper jurisdiction in Montana or Georgia?

Both and possibly Federal jurisdiction applies since it involves air transport.

Your mistaken assumption is that only one jurisdiction applies to any set of events - this is not true. Any jurisdiction can take an interest if their courts decide they can. For example, if the person who died resided in New South Wales, Australia then the NSW Coroners Court could decide they have jurisdiction.

Is it where the accident occurred or where the manufacturer is located?

Yes

Is the proper jurisdiction in Montana or Georgia?

Both and possibly Federal jurisdiction applies since it involves air transport.

Your mistaken assumption is that only one jurisdiction applies to any set of events - this is not true. Any jurisdiction can take an interest if their courts decide they can. For example, if the person who died resided in New South Wales, Australia then the NSW Coroners Court could decide they have jurisdiction. Similarly, if the part in question were made in China then China could claim jurisdiction. All of these claims of jurisdiction are valid and non-exclusive.