The European Court of Justice will rule on Thursday over whether Aer Lingus and Ryanair are liable to pay a multimillion-euro tax bill over the air travel tax which was scrapped by the Government in 2013. The ruling is on separate but similar cases brought by the airlines against the European Commission over its finding in 2012 that a lower tax rate for short-haul flights was unfair. The Commission ordered Ireland to recover the difference between the two taxes — €8 per passenger — from the airlines after it determined in July 2012 that the two-tier tax did amount to illegal state aid. In its action before the Luxembourg-based court, Aer Lingus contested the determination by Brussels, including the commission’s finding that the €10 rate was the “normal” rate. In its case, Ryanair claimed the flat rate of €3 must be considered the “normal” rate and not the €10 rate, which was also unlawful under EU law.