First aerial bombardment by aeroplane

The first time that bombs were dropped from an aeroplane in an air raid occurred on 1 November 1911 during the Italo-Turkish War of 1911–12. Second Lieutenant Giulio Gavotti of the Italian Air Flotilla, threw four small 4.5-lb (2-kg) Cipelli grenades over a Turkish camp stationed in Ain Zara, Libya, from his Taube monoplane which was flying at an altitude of 600 ft (185 m).

Please note, bombs were likely to have been dropped from balloons prior to this, so this record is specifically for aeroplanes.

http://www.aerospaceweb.org/question/history/q0061a.shtml