What factors over time have affected the most common word used to mean "woman who flies a plane"?

I was looking at this thread:
Has the suffix "-trix" acquired a pejorative meaning in recent years?

And I became curious about the popularity of the words aviatrix, aviatrice, aviatress and then later airwoman/airwomen.

I think the Google Ngram Viewer shows some interesting movements:
Google Ngram Viewer

I’m imagining that the bump for airwomen (but not airwoman) was caused by something like the FAA or the Air Force putting out a series of documents that targeted a group and not an individual. Can anyone offer any insight into other things that might have affected the change in preferred verbage for "woman who flies a plane" over time?

Small amounts of research I did found this document from 1991 that used the plural "aviatrices" as well as "AIRWOMEN". However, it also referred to "women pilots" over 40 times. Obviously, this is a small sample size, but it seems to indicate to me that even in 1991 a time when aviatrix was the most common single word, "women pilots" was still far and away the most common phrase ("Aviatrix" never appears in this article). That said, considering the words are synonyms, I feel like the Ngram Viewer should present a more related graph (Either similar bumps due to a rises in popularity of the concept, or troughs for most of the words when one synonym rises at the other’s expense)