The hard part is it has to keep moving, and it has to keep that up for a long time.

The easy part is that it largely keeps itself moving, and that you have a thousand times fewer obstacles to avoid.

Both situations are very hard, and both have very hard aspects that only apply to that situation but not the other one. The plane is not "strictly more difficult".

As a car, finding a safe place to stop in an emergency is over a lot faster than in an airplane, but it's far more dangerous per second and per meter.