Talk to someone who hasn't read the books about The Lord of the Rings and they will inevitably ask you this question, "Hey, you remember those eagles that picked up Sam and Frodo at the end of Return of the King? Why did I have to sit through fourteen hours of hobbits walking when they could have just flown in and wrapped things up in ten minutes?" The short answer: This...
That is called a Fell-Beast and to a Fell-Beast giant eagle tastes a lot like chicken. (A giant chicken, I tell you!) Had they tried to fly into Mordor, they would have had Nazgul all over them before they crossed the Black Gate. Tolkien was explicit about this in the books while Peter Jackson never chose to broach the subject probably because he felt it was mind-numbingly obvious. After all, it was pretty clear that the hobbits only made it to Mount Doom because they were able to travel inconspicuously. But one should never underestimate the stupidity of the movie-going populous, how else can you explain the fact that they are making a Transformers 4 (or the fact that I will probably go see it). So, the eagle question persists.
Let me put this in terms of Where's Waldo, as that is likely the reading level of the people who cleverly think they found a huge flaw in this movie. Trying to find two four foot tall hobbits walking through Mordor while wearing Invisibility Cloaks is like trying to find Waldo in this picture.
Whereas, flying elephant sized eagles through the skies of Mordor is like finding Waldo in this picture.
Well, time is slipping, slipping, slipping into the future, so take us out Steve Miller.
Update: I have gotten into several conversations lately with people who had trouble getting into these films/novels because they found the Ring of Power underwhelming as a MacGuffin. What's a MacGuffin? I'm glad you asked, guy I made up as a literary device. Here is a couple lines from the MacGuffin Wikipedia page explaining what it is and the views of two influential directors: In TV interviews, Hitchcock defined a MacGuffin as the object around which the plot revolves, but as to what that object specifically is, he declared, "The audience don't care".
In contrast, Lucas believes that the MacGuffin should be powerful and
that "the audience should care about it almost as much as the dueling
heroes and villains on screen". I have to agree with Lucas on this one. If the audience doesn't care about the MacGuffin, it means they aren't invested in the story. I also agree with the people who found the Ring of Power unimpressive, but only because the novels did a poor job explaining the true power of the One Ring (and the movies did it even worse). So here is the clear cut explanation Tolkien and Jackson didn't give you: The primary power of the One Ring is not invisibility, it is an amplifier of magical/spiritual powers. In the movies/books, we only ever see the ring used by hobbits so it's essentially just multiplying by zero, but if the ring was on the finger of someone with real power like Sauron or Saruman, it would become a powerful weapon. So that's why it was worth the fourteen hour walk.