When was the first proven act of air sabotage in the history of commercial aviation?

RSVP78, Many crimes were solved in 1933 and before . Not on the microscopic level that is possible now but do not denigrate the efforts of those who worked on this

So here it is the further information It was destroyed by a bomb, with nitroglycerin as the probable explosive agent. A Chicago gangland murder was suspected, but the case remains unsolved.[