History's First Aerial Bombing?

It was not in the Turkish-Italian or Balkan Wars before World War I!

The first aerial bombs in history were dropped from hot-air balloons during the Austrian-Venetian War on 15 July 1849.

The first aerial bombing was attempted in 1849 when the Austrians launched 200 pilotless, bomb-carrying hot-air balloons against forces defending Venice. At the siege of Venice when no position could be found for siege guns, it was decided to use balloons for bombardments. This was during the Italian War of Independence, 1848–1849, when Austrian artillery lieutenant Uchatius undertook the technical development of such a means of attack. Hot-air balloons of thin paper were used. These balloons could carry bombs weighing 33 pounds for a half hour and were dropped by means of a time fuse. The point of departure of the balloons was determined by the direction of the wind. 

Ground Zero for History's First Aerial Bombing

No great material damage was done to the enemy, though one of the charges burst in St. Mark's Square. An unexpected shift of the wind drove some of the balloons back to the besiegers, and their use was abandoned. Aviators would rediscover bombing in the wars that preceded the Great War. In World War II, the Japanese would try to apply Lieutenant Uchatius's idea of using balloons to bomb the west coast of the United States.

Sources:  History of Flight and Smithsonian Institution