Dr. Viirre serves as Volunteer Chief Medical Officer of the Zero Gravity Corporation, the only company in the United States to offer FAA-approved "Zero-G" flights to the public. Through their efforts and those of Dr. Viirre and his medical team, Dr. Hawking, who suffers from the progressive lower motor neuron disease amyotrophic lateral sclerosis (commonly known as "Lou Gehrig's disease") was able to experience weightlessness and freedom from the confines of his wheelchair for the first time in years.