An air transport undertaking holding a valid operating licence or equivalent at the latest on 31 January for the following summer season or on 31 August for the following winter season. For the purpose of Articles 4, 8, 8a and 10, the definition of air carrier shall also include business aviation operators, when they operate according to a schedule; for the purposes of Articles 7 and 14; the definition of air carrier shall also include all civil aircraft operators.