Precise question – kidush or hillul Hashem? You start first with basic halakha – I quoted some above.
My vastly incomplete understanding so far is that the person was not right starting davening standing and also should (rather than can) sit down when told. Again, I did not expect the latter part and not completely sure I am reading this correctly. I would appreciate other opinions.
But, presuming the person was supposed halakhically to sit down and did not, this does not seem to be a kiddush Hashem if it is a violation of ratzon Hashem (aka halakha). It is hilluel Hashem? R Lebowitz who discusses a similar episode in newspapers, even quoting some bochrim who explain that “this was the right thing to do” milder as “not the best moment for the Jewish people” or something like that.
If, on the other hand, he was not supposed to interrupt shmone esre, as most of us commonly assume, then it can’t be Hillul Hashem in that action.
If he could have foreseen the problem, then it is clear from sources above that it is halakhically incorrect and possibly hillul Hashem – caused not by continue standing, but by starting standing. So, interesting nekuda here, that he was an over even before flight attendant came by, so consider her coming as a punishment for the previous aveirah.
In a gray area, where he considered everything and then a wild flight attendant appeared out of nowhere, he may not be over.
Now, an interesting inverted question – if he were to sit down (presuming it is halahkically correct): would that quiet action be considered Kidush Hashem? Or if he would be sitting whole shemone esre?
You can say – how is this kiddush Hashem when it is not in anyone’s face?! (and it is not so inspiring to do a thing that nobody notices anyway, despite Gemorahs saying opposite, like grandson of Choney Hameagel in Tannis who hides from sheluchim his going to daven for rain, pretending that the cloud came by itself)
Possible answer – someone sees other Jews doing it wrong and then sees this guy doing it right and concludes that this is a real Jews following real Torah and now he praises Hashem.