Most often, such a situation occurs due to an aircraft change. In this case, you have the right to request a forced refund of the difference in air ticket cost. To do this, approach the airline's ticket counter at the airport and obtain a voucher for the amount of the fare difference. Later, you can exchange it for cash or use it towards a new ticket with the relevant services of the operating airline.

Please note, if the airline has taken all measures to provide you with priority service (business class meal assortment, provision of front rows in the aircraft cabin, dedicated check-in, boarding, and delivery to the aircraft, etc.), the fare difference can only be refunded through a claims procedure upon your personal application to the operating airline's claims department.