DUBLIN/LUXEMBOURG, Sept 29 (Reuters) - Ryanair on Wednesday said it would appeal a ruling by Europe"s second-highest court rejecting its challenge against an EU order to repay millions of euros in illegal aid given by an Austrian airport. The Luxembourg-based General Court also dismissed a challenge by TUIfly on the same issue. The European Commission in its 2016 decision said certain airport services and marketing agreements between the operator of Klagenfurt airport in southern Austria and Ryanair, TUIfly and HLX - which was merged with Hapagfly in 2007 to create TUIfly - gave the carriers an unfair advantage. The EU competition watchdog said the lossmaking deals amounted to state aid for the airlines as they reduced their operating costs. DUBLIN/LUXEMBOURG, Sept 29 (Reuters) - Ryanair on Wednesday said it would appeal a ruling by Europe"s second-highest court rejecting its challenge against an EU order to repay millions of euros in illegal aid given by an Austrian airport. The Luxembourg-based General Court also dismissed a challenge by TUIfly on the same issue. The European Commission in its 2016 decision said certain airport services and marketing agreements between the operator of Klagenfurt airport in southern Austria and Ryanair, TUIfly and HLX - which was merged with Hapagfly in 2007 to create TUIfly - gave the carriers an unfair advantage. The EU competition watchdog said the lossmaking deals amounted to state aid for the airlines as they reduced their operating costs. It estimated the illegal aid to Ryanair at around 2 million euros ($1.7 million), to TUIfly at 1.1 million and to HLX at 9.6 million. Both Ryanair and TUIfly subsequently challenged the decisions. The Court agreed with the Commission in both cases. Ryanair"s appeal will now be heard by the EU Court of Justice, Europe"s highest. The cases are T-448/18 Ryanair and Others v Commission, and T-447/18 TUIfly v Commission. ($1 = 1.1714 euros)