No, I would not and no, it is not.
I would be more consigned about someone waltzing by while trying to conceal the fact they were armed.
And yeah, you can tell if you know what to look for.
People who are openly carrying are very rarely any danger to others.
So, you feel you have the right to open carry aboard a passenger airplane? An individual with a gun on a plane, openly carried is no problem, right?