Judgment of the Court (Eighth Chamber) of 13 June 2024.#D. SA v P. SA.#Request for a preliminary ruling from the Sąd Okręgowy w Warszawie.#Reference for a preliminary ruling – Air transport – Regulation (EC) No 261/2004 – Article 5(3) – Compensation for passengers in the event of long delay or cancellation of flights – Exemption from the obligation to pay compensation – Extraordinary circumstances – Reasonable preventive measures – Technical failures caused by a hidden design defect – Design defect affecting an aircraft engine – Obligation of the air carrier to have back-up aircraft.#Case C-411/23.