Southwest Airlines will allow only dogs and cats on board their flights as emotional support animals in an update to its service animal policies, the company announced Tuesday. Under Southwest’s new policy, which goes into effect Sept. 17, passengers are permitted one emotional support animal per customer and the animals are limited to only dogs and cats that must remain in a carrier or be held on a leash at all times, according to a statement. Passengers who want to travel with an emotional support animal must present a note from a doctor or mental health professional on the day of departure.