Klass's plasma hypothesis was not well received by those on either side of the UFO debate, who noted that Klass was using one unverified phenomenon—his hypothetical plasmas— to explain another unverified phenomenon—UFOs. The two engaged in a bitter, months-long debate, leveling a variety of charges and accusations at one another. Eventually, Klass wrote to McDonald's superiors at the U.S. Navy (McDonald was formally retired from the Navy, but often worked with the Office of Naval Research), questioning how McDonald could spend so much time on UFO research and still fulfill the requirements for his atmospheric research grant. This did not result in McDonald losing ONR funding but did draw some criticism of Klass from members of the UFO community.