; (3) the number of young children traveling in the same party make it impossible for the air carrier or foreign air carrier to seat all the young children adjacent to an accompanying adult based on the seat layout of the aircraft; or (4) an exception to subsection (b) or (c) deemed appropriate by final rule of the Secretary applies. (g) Definitions In this section: (1) Accompanying adult The term accompanying adult means, with respect to a young child, an individual who is— (A) 14 years of age or older on the date of the scheduled departure of the flight; and (B) on the same reservation record as the young child. (2) Adjacent The term adjacent means, with respect to the seat of a young child, a seat that is— (A) next to and in the same row of the aircraft as the seat of the young child; and (B) not separated by an aisle. (3) Available The term available , when used in connection with seats or seat assignments, means capable of assignment by the air carrier or foreign air carrier without— (A) an upgrade of a young child or an accompanying adult to a different class of service than ticketed