The world’s first flight attendant did not work on an airplane; he worked on a zeppelin.
Heinrich Kubis began his career as a flight attendant before any fixed-wing airliner was large enough to carry a steward and 18 years before Ellen Church of United Airlines became the world’s first steward.
Kubis worked alone on the early zeppelins but had an assistant steward and cook aboard the 20-passenger Graf Zeppelin, and he eventually led a team of 10-15 stewards and cooks aboard the 72-passenger Hindenburg.
(Zeppelin was a large German dirigible airship of the early 20th century, long and cylindrical in shape and with a rigid framework. Zeppelins were used during the First World War for reconnaissance and bombing, and after the war as passenger transports until the 1930.)