Is that the one with the 5th engine mounted behind the cockpit?
http://images.google.com/images?svnum=10&hl=en&lr=&safe=off&q=honeywell+Boeing+720&btnG=Search
Yep, I saw it flying a few weeks back, great to see that in the air!
One website said it was a Northwest plane, but it had a PA tail number, who knows?