‘Observation Balloon’ historical pictures (exact matches)

Observation balloon ascending, World War I
Observation balloon ascending, World War I
A booby-trapped balloon filled with explosive gas ended the career of German First World War …
A booby-trapped balloon filled with explosive gas ended the career of German First World War …
The captive observation balloon in Montmartre
The captive observation balloon in Montmartre
Observation balloon, World War I
Observation balloon, World War I