"difícil de volar" vs "difícil volar"?

[createdamadman]

I've seen both of these examples used in sentences to mean "difficult to fly":


"difícil de volar" and "difícil volar"


I've seen this sort of thing with other words too, and while I know some words must be paired with "de" or some other specific preposition, is it optional in this case? Does using "de" here change the meaning at all?

[Rusty]

We'll need more context to give you the correct answer.
It's important to see the parts of speech.

[AngelicaDeAlquezar]

I agree with Rusty. Context is needed for most constructions.

In the meantime, for this particular case of the verb "volar", the preposition is related to the verb being transitive or intransitive:

If you say "difícil de volar", the verb is transitive. Here, I think about an object that you operate so it flies, like a drone, a plane or a hot-air balloon.
- Los aviones son difíciles de volar. (Planes are hard to fly.)
-> One has to learn many things before one can fly a plane, so it's not an easy task.

If you say "difícil volar", the verb is intransitive. Here, I think of something or someone whose capabilities include flying.
- Para el pájaro es difícil volar si le cortas las plumas de las alas. (The bird will find difficult flying if you trim its wing feathers.)
-> The bird is an animal whose nature is flying, but its capabilities have been reduced when people trim their feathers.