OBJECTIVE: A planet where propeller-driven aircraft are possible and practical and jet-driven aircraft are impossible, impractical, or at best offer no advantages over propeller-driven aircraft (and thus presumably won't be bothered with).
I asked a similar question elsewhere, got mostly bad answers, but one stood out because it was the only one that actually met my criterion of "planetary environmental conditions" and that I couldn't instantly rule out: a planet with suitable elements to build internal-combustion piston engines but lacking useful quantities of suitable elements to make the high-strength alloys needed for practical jet turbines. As others have noted, that seems to be the most likely limiting factor on jet technology.
QUESTION: Is this a viable approach to the stated goal?
That can be broken into two steps.
First, can I actually achieve the desired effect (no jet aircraft) by this method, given known real-world science and engineering, or is there some easy workaround to a lack of said raw materials?
Second, if the premise passes that test, is such a planet (surface) possible AND LIKELY, given what is known about geology and planetary formation?
Piston-engined prop aircraft (or at least turboprop, but I'm aiming for piston). Not electric motors, etc.
Thus, the planet's atmosphere has to support combustion in the first place. It should also support native (assumed oxygen-breathing -- I haven't examined that assumption, but I'd prefer to keep biology comparable to Earth) life. It does not matter whether it can support Earth humans (and I rather suspect it won't).