European Regulation 1107/2006 requires airlines to accept recognized assistance dogs in the cabin or in the hold free of charge. The definition of assistance dogs is specified in ECAC Doc 30, Part I, Section 5: Facilitation of the transport of persons with reduced mobility, June 2012 edition:
“Recognized assistance dog" means guide and other assistance dogs, which are highly trained to assist a wide range of disabled persons with everyday tasks. Guide dogs that are trained primarily to provide mobility assistance to blind or partially sighted people are trained by an organization that is accepted by and affiliated with the International Guide Dog Federation (IGDF). Assistance dogs are trained by an organization that meets the full membership criteria of Assistance Dogs International (ADI).