US Citizen Entering Germany for Urgent Business
 

If you are based in the USA, the best way would be to contact the nearest German mission and ask what supporting documents you need. If possible, ask for a document from them indicating that you would travel for essential purposes.

What is the exact problem? Which commercial products are trying to import into (or out of) Germany?
If you land in Frankfurt (terminal Z or B), then you can skip the regular customs checkpoints alltogether, if you only travel with hand-baggage-only.
However, sometimes customs are setting up random checkpoints closer to the arriving gates.

First of all, the airline will not board you if you don't fall under the category that is admissible into the country under the current Covid-19 restrictions. 2nd, if indeed they let you board, it's not custom that's going to ck your credential for entering the country, it is immigration (passport control) ... So it doesn't matter if you're in Z or B terminal, you would need to go through the passport control before going through custom.

OP is talking about having concerns with customs. Hence, I gave him the best advise possible.
In FRA (as hand-baggage only customer) you don't always have to go through a customs control checkpoint.

Right. Certain regions have strict controls about quarantine, while others don't. Five days seems to be the minimum. Fines can be steep. I'm assuming this is already sorted out.

"Customs" is short-hand, especially in the US, for "passport control".

There is nothing in the OP's context that suggests any concern at all for the import of products.

... for imported goods or what? What are you talking about?

That's exactly right. I'm not bringing anything in other than hand luggage. I am concerned about being able to board, flying to Flughafen Munich, and then being denied entry by passport control. I am working on obtaining a letter of support from the local German consulate and will have letters of urgent business necessity from several business partners. I would like to know if anyone has experience (good or bad) with passport control in this situation. Thanks everyone for your replies.

If the airline allows you to board the flight to MUC then it is very likely that the Bundespolizei will let you pass.
What helps would be written statements by German companies, requesting you to come to Germany for urgent business needs.

I have not done this specifically for business, but have had family come for urgent family reasons (wedding), and had the opposite of flying with my wife and child (german, and both) to America. It basically comes down to how arrogant the check in people are about knowing the rules in my several experiences. Definitely make sure you are at the airport very early for your flight at least 3 hours in case you need to argue with the airline people about your rights to travel. I would make sure you have the correct paperwork worth, as stated above a letter from the german company with as well, and then probably print out the rules from the german government website just as a precaution as well. One trip we even had to have the check in agent in germany call US customs to tell them they were misunderstanding the rules and to let us fly to America (i know you are flying the opposite direction, but same thing applies).

Once you clear the check in process actually entering the countries have mostly been a breeze, a couple of times myself or family members were not even asked for further documentation at the border control once we proved at check in that we were ok to fly. So really, just make sure you are at the airport to check in plenty early and it is usually a breeze travelling.

And how did you manage that? Don't you need a NEI(?) to legally overcome the Schengen Travel Ban?

Non-U.S. spouses and children of U.S. citizens are not subject to the entry restrictions to the U.S.

https://www.whitehouse.gov/briefing-...virus-disease/

... that was not clear from your first post.

Update
 

As an update, I was able to reach the Bundespolizei and obtain pre-clearance of my paperwork to enter Germany. While not a guarantee, it seems unlikely that I would be turned away at this point.