For over a month now I've noticed a 737 (either -100 or -200, I can't tell from the road) parked in back of the Flightcraft business aviation area at PDX and not far from United Cargo. I have no idea if it leaves the airport on a regular basis since I'm only there in the morning, but it is there almost every morning very predictably. It is all white with a dark blue tail and no other markings, no company logo or name, I believe the tail number is N746AP. Unmarked planes at PDX come by occasionally but I figured a 737 is a little big for a GA or business traveler, unless you're Paul Allen in your 767. Anyone know anything about it?
Also, how do you track down this sort of information? All I know about it Flytecomm but it isn't very detailed, often sketchy on information and only lists regularly scheduled commercial flights...for the most part.