Close-up of panel 1. Jack doesn't seem to be a sure-handed inker yet, so there is a lot of white-out in this panel, but that's probably also an example of Jack experimenting with the effects he can create on a page mixing ink and correction fluid.
Notice Jack using the brush to quickly fill in the silhouette of some trees, a common technique perfected by ancient Japanese and Chinese masters of pen and ink, and probably a style Jack learned from looking at other brilliant comic strips, like Milton Caniff's famous Terry and the Pirates.
Panel 2. A synthesis of a lot of styles on the main character. A medieval metallic war helmet, what almost looks like a parachute pack on the back of the vest, and a kneepad. I'd hate to hit rough skies wearing that sword.
Notice Jack is using different textures to give the image variety: thin pen lines for the clouds, cross-hatching on the wall and on the seat, then dark brush-strokes to fill in the blacks. Also a lot of blue-line penciling on the whole piece, maybe Jack trying to add a little 3-dimensionality to the original artwork, although it wouldn't have shown up in reproduction.
Panel 3. Jack needs to work on his lettering. He runs out of room for text at the bottom of the first caption and has to squeeze in the letters so that the whole thing fits.
Nicely delineated airplane. Jack uses a single up-and-down line to hint at the spinning propeller; the plane is fairly realistic, right down to the tiny detail of the pilot's goggles. Again, notice Jack using different textures to hint at the sky with thin parallel lines, then cross-hatching to fill in the mountains below and some of the shadows on the airplane.
Thanks to Stan Taylor for answering my question: What year did Jack draw this comic strip? Stan writes: "I'll take a guess and say late 1937. Jack Curtiss was a non de plume used first by Kirby at Lincoln Publishing. So that narrows it down to 1936- 1939. But Jack's lettering early on was abysmal, the best example would be the Romance of Money pamphlet where the lettering is all over the place. By 1937, the strips begin to feature a more mature, concise and controlled lettering. Always natural, but more precise, as seen in the strips such as Socko the Seadog and Black Buccaneer. But on these strips from early 1937 Jack's narrative prose is usually enclosed in a box while in the sample you provide the text just floats in space- a pattern I see in later Socko strips. I think it's possible that this was a sample strip that Jack did hoping to sell to Lincoln after the Black Buccaneer and Cyclone Burke were cancelled. But I'm just guessing."