For flights longer than eight hours, you must also fill out a form stating your dog can either refrain from using the bathroom on the flight or provide a plan for how they will relieve themselves — such as wearing a diaper or using a pee pad.

Service dogs are highly trained professionals, and on flights shorter than 8–10 hours, they are usually capable of "holding it" for the duration of the journey. However, for ultra-long-haul flights or in the case of an emergency, the primary strategy is for the handler to take the dog into the aircraft lavatory. Owners often carry "pee pads" (absorbent liners) that they can lay down on the bathroom floor for the dog to use, which is then immediately folded up and disposed of in a sanitary bag. Handlers are also advised to strictly manage the dog's food and water intake—typically stopping large meals 12 hours before takeoff—to minimize the need for a mid-air break. At the airport, handlers utilize the mandatory "Pet Relief Areas" (Service Animal Relief Stations) located after security in every major U.S. terminal. According to ADA and DOT regulations, airlines must accommodate these needs, but they can also require handlers of service animals on flights longer than 8 hours to provide "reasonable documentation" that the dog will not relieve itself in the cabin or that it can do so in a way that does not create a health or sanitation issue.