Saw Rev. Jesse Jackson on a flight from DTW to MDW about a year ago. He'd just visited Aretha Franklin after she'd had surgery (Rolling Stone article).

He was in 2C or 3C, just a row in front of me. I was one row behind him in the A seat. Didn't see him in the gate area and didn't notice him when I passed him while boarding, since he was holding an unfolded newspaper. I assume that was deliberate. Anyway, I see a couple of stewardesses greet him and didn't think too much of it. Then a passenger stops briefly to shake his hand. So I finally lean over, discretely, and figure out who he is, just before take off. He kept a low profile the entire flight, as well as after de-planeing. Not sure how many people recognized him.