SAN FRANCISCO, CA – DECEMBER 03: A traveler pets a therapy dog named Toby inside Terminal 2 at San Francisco International Airport on December 3, 2013 in San Francisco, California. The San Francisco SPCA and San Francisco International Airport joined forces to launch a new program called “Wag Brigade” that will have a team of certified therapy dogs that will patrol the airport’s to help calm stressed travelers during the busy holiday travel season. (Photo by Justin Sullivan/Getty Images)