As long as the internal combustion engine is used in aëronautics, and mechanical failure is always a possibility to be reckoned with, the cost of maintaining aëroplane routes, even if they be only auxiliary to dirigible or steamship services, will be greatly swollen by the need of maintaining frequent landing grounds. Every ten miles would be an ideal interval for them; every twenty miles is a minimum for first-rate insurance against risk. From a height of five thousand feet, the probable average minimum elevation for commercial air navigation, a pilot can without difficulty cover a distance of five miles while planing down without the aid of motors. From ten thousand feet he can cover ten miles under the same conditions; so that at this height he would never be outside gliding distance of landing grounds prepared every twenty miles. Given these safeguards, the element of risk in present day aviation is no greater than it was in the early days of railways and steamboats; and little, if any, greater than in modern motoring. Many people, possessing only a newspaper acquaintance with aërial affairs, still believe mechanical flight to be perilous. In exactly the same manner men shunned the infant steamboat, railway train, bicycle and motor-car. Yet, proportionately, the aëroplane and the dirigible are responsible for no more deaths than the train or the automobile. The seeming discrepancy is because so much attention is paid to air fatalities. Every week-end motor-car accidents cause scores of fatalities. Yet the death in harness of a single aviator produces more comment than all of these. Partly, no doubt, the intense horror with which humanity regards death by falling from a great height is due to its novelty among human experiences. The airways of the world offer some pretty problems of international politics, involving commerce, rights of landing, customs duties, air smuggling, air traffic regulations and air laws. All these were dealt with in the International Aërial Commission at the Peace Conference, which agreed upon the following principles: 1. Recognition of the greatest possible freedom of aërial navigation, as far as that freedom of navigation is reconcilable with the principle of the sovereignty of each state in the air above its territory, with the security of the state affected, and in conformity with a strict enforcement of safety regulations. 2. Regulation under obligatory permits for pilots and other aëronautical personnel to be recognized mutually by the signatory states. 3. The establishment of international air rules, including signals, lights, methods of avoiding collisions and regulations for landing. 4. The recognition of the special treatment of army, navy and state machines when on duty for the state. 5. Recognition of the right to utilize all public aërodromes in other states, under a charge to be uniform for the aircraft of all nations, including the home nation.