Randall Monroe points to Titan, Saturn’s largest moon:
Its atmosphere is thick but its gravity is light, giving it a surface pressure only 50% higher than Earth’s with air four times as dense. Its gravity—lower than that of the Moon—means that flying is easy. Our Cessna could get into the air under pedal power. In fact, humans on Titan could fly by muscle power. A human in a hang glider could comfortably take off and cruise around powered by oversized swim-flipper boots—or even take off by flapping artificial wings. The power requirements are minimal—it would probably take no more effort than walking.
But the elements could pose a problem:
It’s 72 kelvin on Titan, which is about the temperature of liquid nitrogen.