You seem to make the implicit assumption that an airline is liable only in situations where it is negligent. That is not the case. There is no requirement to establish negligence on the part of the airline to establish liability for compensation under Reg 261/2004 nor is it a defense to such liability for the airline to establish that it was not negligent. The test is as defined in Wallentin-Hermann, namely that the technical problems "stem from events which are not inherent in the normal exercise of the activity of the air carrier concerned" (as well as, in addition, being beyond its actual control). The examples gien by the ECJ of such events that could be regarded as being outside the normal exercise of the activity are such things as a hidden defect "revealed by the manufacturer of the aircraft comprising the fleet of the air carrier concerned, or by a competent authority" (think: the 787 batteries issue as a typical example of that) or damage resulting from sabotage or acts of terrorism.

Whether "ordinary" ground damage could be regarded as sufficiently "extraordinary" to warrant exclusion of liability is not clearly established at this stage. I would point out, in addition, that we do not know either who played what role in the damage. If there was a piloting error, for instance, it would clearly not constitute an 'extraordinary circumstance' within the meaning of the Reg since it would not be outside the airline's control.

I must say, incidentally, that I do not see the problem with making the airline liable in that situation, since they should in principle be able to turn to whoever is responsible for the damage to reimburse them of what they have to pay to the passengers.