If someone had quietly pointed out that there are reasons beyond the current US sanctions to ban Mahan Air it may have happened... but now that it is public. No way.
In the case of W5 specifically, they have been noted to (along with 6Q - Cham Wings) have carried out flights at odd times to and from Syria with almost no passengers but full of munitions in the cargo hold, and are acting on behalf of the IRGC as well as Hezbollah and Hamas in support of their terrorist activities, all of which are formally designated foreign terrorist organizations by the US Department of State. W5's Malaysia-based sales agent, Mahan Travel and Tourism Sendirian Berhad, is also under official Treasury sanctions for the same reason, being used to evade banking sanctions.
Come to think of it, I have to imagine that the USA has tried to reason with the EU, but the EU has turned a deaf ear. The idea is that W5 is using its aircraft to covertly support terrorism and that pressure is being put on Germany to potentially seize W5 aircraft landing in Germany (their current destinations there are DUS and MUC, and it needs German airspace to access BHX).
I'm not sure if an airline has ever been designated a foreign terrorist organization, but that may be the next move.
I always enjoy reading your well-thought out responses aemoreira! You clearly state the facts, which is much appreciated.
In my opinion, regardless of politics, an airline that provides support to terrorist groups should be banned. It's a no-brainer. Grenell didn't call for the end of Iran Air flights or Lufthansa flights. He specifically mentioned Mahan Air. That is because Mahan Air has been shown to support terrorist groups. With that said, why would anyone support the airline?
People don't have to hate everything Trump, or a Trump appointed person, does just because of the association with Trump. This is about stopping material support to terrorist groups. It should be of concern to the whole World, and especially Germany since they have had their fare share of terrorist attacks also.
And finally, to all those saying Richard Grenell has no say in European matters: Hate to break it to you, but that is kind of his job. The job of any diplomat is to be the official liaison of the United States to the host country. They are there to project American ideas and ideals to the host country. Sure, the host country isn't required to accept or implement the ideas, but it is still the diplomat's job to represent American interests in Germany.