They are not notable for the mere fact that Truthers are hostile to the theory. They are notable because some Truthers proposed this theory and it was covered in various news outlets, discussed on virtually every conspiracy theory website, etc. As the article here points out, many Truthers are hostile to this theory, which is notable, but's not the primary reason the no planes theory is notable. So, again, I agree it should be included in the Truthers article, but it certainly shouldn't be removed from this one.