Where, in accordance with Article 108(3) TFEU, the Commission has initiated a formal investigation procedure with regard to an aid measure which has not been notified and is in the course of implementation, a national court hearing an application for the cessation of the implementation of that measure and for the recovery of the sums already paid is required to adopt all the measures that are necessary in order to draw the appropriate conclusions from any infringement of the obligation to suspend the implementation of that measure. To that end, the national court may decide to suspend the implementation of the measure in question and order the recovery of the sums already paid and, possibly, decide to order interim measures in order to safeguard, first, the interests of the parties concerned and, secondly, the effectiveness of the Commission’s decision to initiate the formal investigation procedure. Thus, the obligation to suspend the implementation of the measure in question is not the only legal effect of such a decision. Consequently, a public body which formerly held the rights in the undertaking owning an airport remains exposed, after the privatisation of that airport, to the risk that a national court might order the recovery of any aid granted during the period for which that public body held the rights in the undertaking owning the airport that is subject to the measure at issue. Accordingly, in the absence of a final decision of the Commission closing the formal investigation procedure, the effects of a decision to initiate a formal investigation procedure endure, so that the public body retains an interest in bringing proceedings seeking the annulment of that decision.

The mere fact that the schedule of charges of a certain airport applies only to airlines using that airport is not relevant for the purpose of finding that that schedule is selective.

It certainly does not follow from the case-law of the Court that a measure by which a public undertaking lays down the conditions for the use of its goods or services is always, and therefore by its very nature, a selective measure for the purposes of Article 107(1) TFEU.

On the contrary, that provision does not distinguish between measures of State intervention by reference to their causes or their aims but defines them in relation to their effects, and thus independently of the techniques used.

Accordingly, whilst it cannot be ruled out that a measure by which a public undertaking lays down the conditions for the use of its goods or services is selective despite applying to all the undertakings using those goods or services, it is necessary, in order to determine whether that is the case, to have regard not to the nature of that measure but to its effects, by examining whether the advantage which it is supposed to procure in fact benefits only some undertakings as opposed to others, although, in the light of the objective pursued by the regime concerned, all of the undertakings are in a comparable factual and legal situation.

Thus, a State measure which benefits only one economic sector or some of the undertakings in that sector is not necessarily selective. It is selective only if, within the context of a particular legal regime, it has the effect of conferring an advantage on certain undertakings over others, in a different sector or the same sector, which are, in the light of the objective pursued by that regime, in a comparable factual and legal situation.

Accordingly, the fact that a certain airport is in direct competition with other national airports and that only airlines using the former airport benefit from any advantages conferred by the abovementioned schedule of charges is not sufficient to establish that that schedule is selective. In order for the schedule to be selective, it would have to be established that, within the context of a legal regime under which all those airports fall, that schedule confers an advantage on airlines using a certain airport to the detriment of airlines using the other airports which are, in the light of the objective pursued by that regime, in a comparable factual and legal situation.

(see paras 46-49, 58, 59)