It has come to my attention that Winston Churchill's first transatlantic flight made him a temporary target of both sides when the plane was flown
quite a bit south of the intended route. (see the last few paragraphs of the blurb).
WWII is overdone, but having Churchill die in a tragic accident seems like one of the slicker ways to change things. The effects are also likely to be subtle rather than done with a hammer. It might be a fun way to make a "lightly tweaked" alternate.
I'm not sure who would have replaced him. Is anyone fluent in that sphere of history?