Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. US Tightens Definition of Service Animals Allowed on Planes Associated Press The Transportation Department issued a final rule Wednesday covering animals on airlines. It decided that only dogs can fly as service animals, and companions that passengers use for emotional support don't count. The rule aims to settle years of tension between airlines and passengers who bring their pets on board for free by saying they need them for emotional help. Under a long-standing department policy, all the passengers needed was a note from a health professional. Airlines argued that passengers abused the situation to bring a menagerie of animals on board, including cats, turtles, pot-bellied pigs and, in one case, a peacock. .