The invention of wireless telegraphy and recent improvements in the aeroplane and dirigible balloons have greatly extended the possibilities of international aerial communication and navigation, and have thus rendered necessary a discussion of the law of the so-called aerial domain in works on international law.During its session at Ghent in 1906, the Institute of International Law adopted the following principles: “The air is free. In time of peace and in time of war, states have over it only the rights necessary for their self-preservation.” These principles, which were based upon the views of Fauchille and accepted by a vote of 14 against 9, have been justly criticized. They are not in agreement with recent articles and monographs on this subject, and do not answer the practical necessities either of aerial navigation or wireless telegraphy, especially in time of war.