This follows a judgment by the General Court on 25 November 2014 (case T-512/1) annulling the Commission's 2011 findings that the exclusion of transfer and transit passengers did not result in state aid. The Court held that the Commission should have initiated the formal investigation procedure in order to gather any relevant information to verify whether the disputed measure was selective and allow interested third parties to present their observations. The Commission will now investigate whether the tax exemption provides certain companies with a selective advantage, in breach of EU state aid rules. The investigation will examine in particular whether the exemption serves to avoid levying the tax twice on the same journey, and whether exempting transfer flights only when they were booked in a single-booking discriminates airlines not applying a single-booking policy. The opening of an in-depth investigation gives interested third parties an opportunity to submit comments. It does not prejudge the outcome of the investigation.