Conversation so far:
When did Walter Cronkite start his career?
In 1936.
what was walter cronkite's job?
Walter Cronkite entered broadcasting as a radio announcer.
what newspaper did Walter Cronkite write for?
In 1939 Walter Cronkite became a news editor for United Press.

Question: when was he first on air?
Self-contained rewrite: when was walter cronkite first on air?