Sky Girl is chloroformed by some thugs who then take her onto a plane. The chloroform scene is very brief and we don't see the cloth. Sky Girl is carried over the shoulder.
Flash Gordon is kidnapped, and Dale Arden is chloroformed when trying to save him.
The cover shows Dale unconscious. Rare issue. https://www.comics.org/issue/57189/
This is the first scene in the sleepycomics.com database.
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Contributed by succubi