Judgment of the Court (Grand Chamber) of 2 April 2020.#Caisse de retraite du personnel navigant professionnel de l'aéronautique civile (CRPNPAC) v Vueling Airlines SA v Vueling Airlines SA and Jean-Luc Poignant.#Requests for a preliminary ruling from the Tribunal de grande instance de Bobigny and Cour de cassation.#Reference for a preliminary ruling — Migrant workers — Social security — Regulation (EEC) No 1408/71 — Legislation applicable — Article 14(1)(a) — Posted workers — Article 14(2)(a)(i) — Person normally employed in the territory of two or more Member States and employed by a branch or a permanent representation that an undertaking has in the territory of a Member State other than that where it has its registered office– Regulation (EEC) No 574/72 — Article 11(1)(a) — Article 12a(1a) — E 101 certificate — Binding effect — Certificate fraudulently obtained or relied on — Power of the courts of the host Member State to make a finding of fraud and disregard the certificate — Article 84(a)(3) of Regulation No 1408/71 — Cooperation between competent institutions — Authority in civil proceedings of res judicata in criminal proceedings — Primacy of EU law.#Joined Cases C-370/17 and C-37/18.