My copy has a date also.
Butler mentions Don Dwiggins' book, "They Flew the Bendix Race" at the beginning of the section. I presume she's paraphrasing from his book, as there are no footnotes in this section. In the Notes section for that chapter Butler cites Louise Thaden, "High, Wide, and Frightened", p 184 and Blanche Noyes, Columbia, OH, p. 22. (Butler, p. 437)