I don't know if it's still the case, but until a year or two ago at least, you could walk through SFO and pick out bits and pieces of United signage / branding from the Saul Bass era -- a visual identity theoretically retired when Stephen Wolf's Death Star look came in in the early 1990s. United never made crisp, uniform branding any kind of priority.

They did change the master brand compulsively though -- six distinct looks 1970-2019 (Friend Ships, Bass / tulip, Death Star, overscanned tulip post-BK, hybrid meatball, evolved / recolored meatball II) -- a period when American deemed the number of necessary livery changes to be one.