I keep seeing a theory about how Gandalf was supposedly planning on flying the One Ring into Mordor. I won’t deign to link to the article, but here is why that could never work:
The Eagles were never an option for taking the Ring to Mordor. The Eagles are never mentioned as a plan because it would be even more absurd than trying to sneak into Mordor already was. It has the same chance of success as a plan to “simply” form an army and march into Mordor.
When Gandalf is imprisoned by Saruman, he doesn’t, “think to get the eagles help him escape”. The Eagles were already looking for Gandalf due to the plan set in motion by Radagast earlier in the book. When Gwaihir went to bring the news of his findings of the Enemy’s movements to Gandalf, he obviously noticed it was more important to rescue him than to simply deliver a message. Gwaihir thus flies Gandalf to Rohan, where he gets a horse at Meduseld and rides back to Eriador to find Frodo and get aid from Elrond. Gwaihir even specifically mentions that he can’t travel a great distance with Gandalf because people are heavy and flying is hard, which is why Gandalf is only flown as far as Rohan and not all the way back to Rivendell.
Next, the creator of the theory seems to indicate that the Eagles are worried about the plan being found out and, “having to fight the Nazgûl.” Assuming he actually means Nazgûl riding on fellbeasts, they haven’t yet been revealed by Sauron, so it would be a nonissue at that point. Regardless, thinking that Sauron wouldn’t have the means to repel an incredibly obvious attempt (it’s rather hard to hide in the sky) is crazy. We read in The Hobbit that the Eagles are reluctant to go near human settlements for fear of being shot down with arrows. Well, I’m quite certain that Mordor has more archers and arrows than some small settlement in Rhovanion.
The notion that Gandalf won’t even trust Elrond with this plan is idiotic. We’ve already established that Gandalf specifically went to Rivendell to get help.
There are no orc infestations in the High Pass. As we hear, that area was kept clear by Beorn’s people. The High Pass, like Caradhras when they get to it, is infested with winter. Caradhras does not have a storm summoned by Saruman. If we accept that the bad guys can see where the Fellowship is going, how could they ever secretly turn north to head to the Eagles. This means they should have gone over the High Pass, since their turning north would give their enemies less time to prepare (since they would have to go less north). Even by the movie plot, the theory breaks down.
Finally, ‘Fly’ means flee. Unless someone is actually flying, fly means flee. Flee quickly. You can look this up in a dictionary. If you’ve read the books, you can see Tolkien use the word in this way frequently, including three sentences later, when Aragorn and Boromir, who had charged toward Gandalf’s standoff and were on the bridge, come ‘flying’ back, doing exactly what he told them to. At this point, we affirm that the writer has never read the books, and quite possibly has not touched a dictionary either.