Of the 350 machines constituting the American air raid on Wavrille in October, 1918, only one aeroplane failed to return, though twelve Hun machines were shot down. The German flying-tank which shot down Major Lufbery, the most famous American ace, was driven by five engines, which were protected, as well as the fuselage, with bullet-proof steel three-eighths of an inch thick. Major Lufbery emptied his machine-gun against this aerial monster from close range and from many angles before his gas-tank was pierced and his machine went down in flames. Therefore a bimotored machine, flying under peace conditions, should be able to make its aerodrome safely nearly every time. There were three discomforts of air travel—the cold, the noise of the motor, and the lack of room in moving about. Electrically heated clothes eliminate the cold; ariophones, which shut out the noise of the motor but permit the passengers or aviators to converse together, are in universal use on aeroplanes. With the increase in the size of the aeroplanes and the number of motors, the nacelles and the enclosed roomy cabins can be constructed as they were on the famous Sykorsky aerobus, which was built in Russia before the war. This aeroplane carried twenty-one people to an altitude of 7,000 feet. On this trip they had ample room to move about and to observe the sky and the landscape. On Thanksgiving Day, 1917, a half-dozen guests of an American aircraft factory had their turkey dinner served in a huge aeroplane above the clouds. The Handley Page and Farman aerial transport busses now flying between London and Paris carry the passengers entirely housed in. It is true that owing to the cost of the aeroplanes and the aeromotors, their upkeep and the number of skilled men required to fly and maintain them, all aerial travel is expensive. The two-seater training-machines, equipped with one motor, cost five to seven thousand dollars, and the huge bimotored bombing-machines averaged forty to sixty thousand dollars. This price was due to the necessity for hurried construction. For everything that went into the building of the aeromotor and the machine itself and also for the labor the very highest price had to be paid. Tools, machinery, factories, fields, hangars, and a thousand other things had to be purchased, and a great body of skilled workmen had to be trained before aircraft could be turned out in quantity.