Not quite sure which thread it was, but someone was asking whether the feds did a good search of the Portland airport area to see if anyone saw Cooper arrive at the airport. I think it was Himmelsbach (I could be wrong, and pls don't make me look for it right now, eyes adjusting to new contacts)who stated that search was very thorough, taking in everything from bus, taxi, and car rental services to restaurants, hotels, motels, and possibly henhouses and outhouses in the area. Nobody recalled anyone matching Cooper's description.
Of course, it is entirely possible that Cooper simply stepped off another plane. I don't know whether the feds would have checked ARRIVALS at Portland who did not have connecting flights. Cooper didn't, if he did arrive by plane; he bought his Seattle ticket at Portland in cash.
Wherever he was before buying that ticket, he doesn't seem to have done anything that would attract any attention. I'm guessing, then, that he didn't really "lounge" anywhere in the airport for any noteworthy period of time.
Anyway, that's really my only input on that. I do recall reading the feds checked service providers of all kinds in the area pretty thoroughly - even shoe shine people.