If you judge what people might do because of the way in which they are dressed, that is a type of prejudice. You are pre judging someone based on what is probably an unrelated observation.
If I were in charge of NPR I do not think his remark justifies firing him. It was an honest observation, even though it did reveal a prejudice on his part.When I see someone in Muslim garb, I do notice it, and I do make note of where they sit on the plane, but I don;t do anything other than that.
When I get on a plane, I try to guess who might be an air marshal. I have only identified one that I am reasonable certain in the last ten flights. I suppose that this is a sort of prejudice concerning dress as well. Still, the twenty-year old woman with the tattoo: NOT am air marshal. The guy wearing flip-flops and plaid shorts: not him, either, nor any of the grannies and grampaws.
If I were a Muslim, I would not dress like one when I flew anywhere. I suppose a Sikh might wonder where to hide all his hair without a turban, but I know that a Sikh is unlikely to be a terrorist.