To continue my thought earlier that the early Mickey Mouse animated cartoons must have been a mutual influence on both strip cartoonists. . .
I've just watched an early
Mickey Mouse short cartoon,
Plane Crazy, from 1929, in which Mickey is inspired by the recent fame of Charles "LIndy" Lindberg to build and fly a plane.
There's a sequence where Mickey (trying to impress his passenger Minnie) loops the loop. Minnie falls from her seat at the top of the loop but falls back into her seat as Mickey bottoms out of the loop - exactly the same accidental stunt we see the Thom[p]sons perform in
The Black Island, as well as being similar to the Gottfredson strip pilot-catching sequence you describe, Lurker.
Of course
Plane Crazy (and both subsequent strips) was directly influnced by the exploits and stunts of
real barnstormer pilots of 1920's America (including Lindberg in his younger days).
Some of these barnstormers did specialize in climbing from one plane to another in mid air, notably
Gladys Ingle, though I don't think anyone actually performed the stunt of falling from a loop-the-loop and being caught in the same plane! (And I think the forces from the manoeuver would counteract gravity and hold you in your seat during the loop anyway.)
Anyway if
Plane Crazy is the first fictional example of this stunt, I guess we should credit the gag to Walt Disney, or more properly at least co-credit it to that film's director, Walt's rather overlooked top animator and co-creator of Mickey Mouse, Ub Iwerks.
There may well be other similar examples of stunts and gags in the early Mickey Mouse animations influencing Hergé and Gottfredson's comics. For instance Hergé's Ranko seems to owe quite a lot to Bebbo the Gorilla, who appeared in at least a couple of these early Mickey Mouse animated shorts.
The original
Mickey Mouse films would obviously have been an expected and required influence on Gottfredson, but they were probably an inescapable influence on
anyone producing cartoon comedy-action sequences at the time, given how popular and groundbreaking these early
Mickey Mouse animations were.
Hergé was a bit of a magpie generally, but I agree that he adapted his influences and sources into his own work with enough originality and uniqueness for us to call it homage rather than plagiarism!