I fly for Mesaba and have jumpseated on NW mainline 3 or 4 times now with absolutely no problem. In fact the other day, I jumpsteated LGA-MSP with an AWAC guy. Interestingly, we both sat in the back as Mr. Doug Steenland (I think thats how you spell it) rode in the jumpseat. He was on the Today Show that morning and probably didn't want to face pax in the back. I have never actually jumpseated on one of my own flights, but I don't think it would be a problem unless weight-restricted.