system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so difficult for us to just replicate a bird instead of the kind of fixed wing aircraft we have?
gpt
Flapping bird wings are kind of inefficient. They're great for picking yourself off the ground, but require a lot of energy to keep going 

Larger birds, which are still small and light compared to an airplane, achieve flight easier by riding updrafts in the air and gliding, with very little flapping at all.

This is what the fixed wing aircraft replicates. This has added benefits of less turbulence, with the plane not being pushed up by the periodic addition of lift.