I flew on Continental to and from Peru last year. I had my empty fuel bottle, and stove (used, not new) packed in the middle of my backpack. I was able to check my bags, no problem. I was a little wary about having it in a carry-on, but found no problem checking it. They could be just covering themselves, so they don't have to make sure people have them empty, they just tell people they can't bring them...