results in an undue burden on the ability of a young child to receive an advance seat assignment adjacent to an accompanying adult. (c) Additional requirements for advance seating (1) In general Subject to subsection (f), an air carrier or foreign air carrier that allows individuals to select seats or that assigns seats at the time of booking a flight shall provide, not later than 48 hours after the issuance of the ticket for each young child— (A) a seat assignment for the young child adjacent to the seat assignment of an accompanying adult for each flight segment of the ticket at no additional cost, provided that adjacent seat assignments are available