In less than one month, Russian aircraft have violated the airspace of three member states – Poland, Romania and Estonia – putting the continent on high alert. Advertisement AdvertisementAdvertisement Advertisement"The latest attacks in Romania, in Poland, in Estonia, now in Denmark, four member states have been targeted. This is precisely why we will be working on this drone wall." 'Russia is testing the European borders'It remains unclear how the drone wall might work in practice and what costs it might incur. Regnier did not specify the launch date of the drone wall but noted: "Recent events show that we cannot sit here and wait for things to happen before we need to act."