Judgment of the Court (First Chamber) of 19 October 2023.#MK v Lufthansa CityLine GmbH.#Request for a preliminary ruling from the Bundesarbeitsgericht.#Reference for a preliminary ruling – Social policy – Part-time work – Directive 97/81/EC – Framework Agreement on part-time work concluded by UNICE, CEEP and the ETUC – Clause 4.1 – Principle of non-discrimination of part-time workers – Principle pro rata temporis – Pilots – Remuneration for additional flying duty hours – Identical trigger thresholds for full-time and part-time pilots – Difference in treatment.#Case C-660/20.