Zeppelins
Not to be confused with the great band, zeppelins were used for bombing populated areas such as London. Germany used zeppelins first and it was used apon citizens and troops alike. The zeppelins were massive blimps that when flying over-head of someone they would drop bombs. Zeppelins caused major advances for the german army, but did not bring them to winning the war.
Zeppelins were never used again after this war with planes, jets, and helecopters advancing and becoming a main source of air travel. Zeppelins also were put to rest due to incidents that could happen. The very flamable gasses could light at any moment due to smoking being allowed within the zeppelins (only in a pressurized room) and the Hendinburg incident.