The aim of the service is to have therapy animals at the airport to destress passengers according to Jessica Ramirez, the office manager for Pets Unstressing Passengers (PUP).
Ramirez said that it's been "proven" that when travelers who are nervous and on edge see the dogs "they relax" and are not so worried or so angry.
"The children can entertain themselves and (the adults) have a little time to rest," she said.
The San Jose, California, airport was the first to bring in hospital and nursing home therapy pets to help its passengers, starting the programme after the September 11, 2001, terrorist attacks, when people were afraid that their aircraft could be hijacked by terrorists.
At Los Angeles International Airport, the country's second-busiest, therapy dogs are being used more than ever because stress has increased due to remodeling work that is forcing employees to work extra hours and making many passengers unable to easily find the check-in locations for their flights.
PUP director Heidi Huebner said that using the therapy dog service helps passengers, particularly those who are flying for "sad reasons," such as the death of a loved one.
At the San Francisco International Airport (SFO), the therapy pets are called The Wag Brigade and are managed by volunteers coordinated by the American Society for the Prevention of Cruelty to Animals.
"We want the experience at our airports to be enjoyable, and so we wanted to include the therapy animals so that the trip would be less stressful," Doug Yakel, SFO spokesman, said.
Yakel emphasised that there are 30 dogs in the Brigade, including "Lilou, the little pig," who sparks "surprised" reactions from passengers.
Meanwhile, 32 ponies are being provided to the Cincinnati/Northern Kentucky International Airport, and Seven Oaks Farm Miniature Therapy Horses president Lisa Moad said that "when passengers pet the horses, their heartbeats slow and blood pressure drops, the brain produces more serotonin ... the people are happy, friendly and smiles appear."