During the great advance of the Allied troops in France in March, 1917, unusual activity in the air played an important part. This was especially the case on March 17, 1917, when the British either destroyed or damaged sixteen German planes, the French ten, and the Germans accounted for a total of twenty-two British and French machines. At this time aeroplanes were active not only in reconnaissance work, but even attacked with bombs and machine guns smaller units of the retreating Germans. The British official report covering March 18, 1917, for instance, contains the following passage: "Our aeroplanes did much valuable work yesterday in cooperation with our infantry. Enemy troops were engaged successfully with machine guns, and bombs were dropped on a number of places behind the enemy lines," while the French report says: "During the evening of March 17 and the following night a French air squadron bombarded the factories and blast furnaces at Thionville and in the Briey Valley, as well as certain convoys of enemy troops which were marching in the region of Guiscard."
The same kind of aerial activity was an almost daily occurrence during April, 1917. The last days of that month, however, were red-letter days for military aeronautics. On April 29, 1917, the British claimed to have winged twenty German machines, while the Germans stated that they had shot down during April 28 and 29, 1917, a total of thirty-four British and French planes.
Again on May 7, 1917, the British accounted for fifteen German machines, while the French claimed to have brought down during the week May 1 to 7, 1917, seventy-six German aeroplanes, of which twenty-five were known to have been destroyed.
During the last days of May, 1917, Allied aeroplanes were especially active in Belgium. On May 26 and 30, 1917, Hest, Blankenberghe, Zeebrugge, and Ghent were attacked and considerable damage was inflicted on railway stations, docks, and other buildings of military value.
Again on June 4, 1917, British aeroplanes attacked and severely damaged German vessels in Zeebrugge.
French airmen were busy, too, in June, 1917. The French War Office on June 21, 1917 published the following statement covering their activities:
"Fourteen aeroplanes and a German captive balloon were destroyed on our front in the period from June 8 to 20. Eleven of these machines were brought down by our pilots during aerial combats, and three of them by the fire of our machine or antiaircraft guns. In addition, seven enemy machines seriously damaged fell in our lines.
"In the same period our squadrons effected numerous sorties. They bombarded notably the railroad station at Bensdorf, factories at Hayatge-Jesuf at Moyeuvre, blast furnaces at Burbach and in the Saar Valley, railroad stations at Bethienville, Châtelet-sur-Retourne, Bethel, Mezières, Charleville, and Molshelm; the bivouacs in Suippes Valley, and munitions depots in the region of Laon, etc. Thirteen thousand kilograms of projectiles were dropped during the expeditions, which caused serious damage to enemy establishments."
British, French, and German air squadrons continued their activities throughout June and July, 1917. July 12, 1917, was particularly successful for the British airmen, who claimed to have brought down near Ypres thirty-one German planes without loss to their own forces.
On the Russian and Italian fronts and in the Balkans and the Near East aerial activities were slightly fewer and less extensive than on the western, due to the difference in conditions, such as the greater scarcity of machines and the greater distance from the source of supplies.