I tried that when I was a kid. I found that the heat needed to generate lift was greater than the heat needed to melt the plastic. Of course, I was using a thin cardboard frame (made of punchcards from the computer lab, IIRC) but I think it would be pretty difficult to get this to fly without melting it. (And a burn from molten plastic is nasty - I have a round scar on my left hand that's still visible, a quarter of a century afterwards. <img src="images/graemlins/blush.gif" alt="" /> )