Have you ever looked up at the sky, seenaw a bird flying, probably hundreds of feets above you, and wondered what it would feel like to be that bird?

"Saw" is typically used when it's connected to a pronoun - like the "you" at the start of the sentence. "Seen" isn't used as a standalone verb - it's connected to verbs like "have" or "was".

I think that's pretty common, because they look so free up there, and they also have that great view of nature while they continue to travel across the sky.

Your sentence is grammatically correct, but removing "continue to" makes it seem less stiff/formal.

IOn the number ofmany occasions thatwhen I've thougtht about that, the first thing that comes to mind is the places that I could go.

"Number of" is grammatically fine, but it's more ambiguous and formal than "many", if that's what you meant.

If there iwas any place I wanted to go, I could just use my flying powers and get there in minutes or hours without paying anything.

The tense in the first half of the sentence didn't match the second half.

Also, I would be able to go to places that normally a plane or anyone else normally wouldn't take me, like a desert island!

I should be careful about the scientists, the government, and the air traffic towers though...

You don't need "the" for scientist(s) unless you're talking about specific scientist(s).

Have you ever looked up at the sky, seenaw a bird flying, probably hundreds of feets above you, and wondered what it would feel like to be that bird?

In the number of occasions that I've thougtht about that, the first thing that comes to mind is the places that I could go.

Also, I would be able to go to places that normally a plane or anyone else wouldn't normally take me, like a desert island!

I should be careful about the scientists, the government, and the air traffic towers though...