(1) The traveller may declare on a durable medium, within a reasonable time limit prior to the start of the package, that a third party accedes in their stead to the rights and duties under the package travel contract. The declaration in any case is considered to have been made in due time if it is received by the organiser no later than seven days before the start of the package.
(2) The organiser may object to such accession to the contract by a third party if the third party does not satisfy the contractual travel requirements.
(3) Where a third party accedes to the contract, then the third party and the traveller are liable to the organiser as joint and several debtors for the price of the package and any increased costs resulting from the third party acceding to the contract. The organiser may demand a refund of additional costs only if and to the extent these are reasonable and the organiser in fact has incurred them.
(4) The organiser is to provide proof to the traveller of the amount in which additional costs have arisen as a consequence of the third party acceding to the contract.