During his career, which included a 20-year stint at Leo Burnett, Tennant worked on strategy for brands such as Kellogg's, Nestle, Campbell's Soup and United Airlines.
He was employed variously as a creative director, copywriter, composer, commercial director, editor, artist and filmmaker.
Tennant got his start in advertising in 1950, when he joined Leo Burnett in Chicago. His credits include writing the original radio and TV campaign for the launch of Marlboro cigarettes in 1955 and inventing Tony The Tiger for Kellogg's Frosties in 1952.
Another of his famous creations was United Airlines' "Fly the friendly skies of United" tagline, which was used from the mid-1960s until the mid-1990s.
Tennant died at his Los Angeles home on Saturday.
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