We're lucky enough to live on a planet where it's comparatively easy to design and build airplanes that work: our atmosphere and the Earth's gravitational pull are kind in that respect. But what would happen if you tried to fly a regular plane around another planet or moon?
As Randall Munroe points out in a new What If? post, in most cases, not a lot: there's no atmosphere on plenty of those celestial bodies, so a plane would fall straight out of the sky. On the few that do have an atmosphere—including Mars, Venus, the four gas giants, Saturn's moon Titan, and the Sun—it's more difficult to say.
So Munroe took to X-Plane, a highly tweak-able flight simulator which accurately models flight physics in-game. It's so tweak-able, that it can simulate flight on other planets. So... that's what Munroe did. His results, which you can read over on What If?, are entertaining:
Our Cessna can't fly on Jupiter; the gravity is just too strong. The power needed to maintain level flight is three times greater than that on Earth. Starting from a friendly sea-level pressure, we'd accelerate through the tumbling winds into a 275 m/s (600 mph) downward glide deeper and deeper through the layers of ammonia ice and water ice until we and the aircraft were crushed. There's no surface to hit; Jupiter transitions smoothly from gas to solid as you sink deeper and deeper.
But there is one piece of good news. On Saturn's moon, Titan, a relatively low surface pressure and insanely low gravitational pull (weaker than our moon's), means even a pedal-powered plane could take off. You can—and should—read the whole post over on What If? ... and then maybe take a flight to Titan. [What If?]