At the end of the film adaptation of The Return of the King, three Eagles swoop down from out of nowhere to rescue Sam and Frodo from the slopes of Mount Doom as it spews out lava and ash after the One Ring has been destroyed.

A common critique of the film is that if the Eagles could have rescued Frodo and Sam, they could also have carried the One Ring to Mount Doom, thus cutting the story short and simplifying the plot.

This thought was in my mind as I read both The Hobbit and The Lord of the Rings recently, as I believe I discovered ample textual evidence to support the assertion that the Eagles could NOT have carried the One Ring to Mount Doom, even though neither the text nor Tolkien himself explicitly make that claim.

1. The Eagles are not concerned with the affairs of other races.

In The Hobbit, the narrator gives some background information on the Eagles, explaining that they are not terribly concerned with the affairs of other races, preferring to keep to themselves in their aeries in the Misty Mountains. They stayed away from the realms of men for practical reasons--men tended to shoot first and ask questions later when Eagles snatched their livestock. When the Eagles rescue Thorin and Company from goblins in the Misty Mountains, Gandalf attempts to persuade the Eagles to take them closer to the Lonely Mountain and is met with this response:

The Lord of the Eagles would not take them anywhere near where men lived. "They would shoot at us with their great bows of yew," he said, "for they would think we were after their sheep. And at other times they would be right. No! We are glad to cheat goblins of their sport, but we will not risk ourselves for dwarves in the southern plains."

"Out of the Frying-Pan into the Fire," The Hobbit

It's doubtful that the Eagles would see the need to carry a tiny trinket like the One Ring to Mount Doom. It's simply not a part of their world.

Mordor was crawling with Orcs, Goblins, Men, and other nasty beings who would gladly shoot down any Eagle attempting to penetrate their defenses. Sauron even had flying defenders in the form of "fell beasts" that later served as mounts for the Nazgúl.

2. Secrecy was of primary importance.

Above all, the One Ring had to be carried to Mordor in secret. That meant the Enemy had to be fooled. Eagles tend to stand out. Especially when Eagles are found in territory where they don't belong. And not all Eagles are good. Many of them could, in fact, be spies for the Enemy.

Eagles are not kindly birds. Some are cowardly and cruel.

"Out of the Frying-Pan into the Fire," The Hobbit

It's made quite clear that Sauron has many, many flying spies between Mordor and the Misty Mountains. The Fellowship has to hide from such spies more than once on their travels through Eregion.

During their trip down the Anduin, both Legolas and Aragorn make note of an Eagle flying high and they wonder on whose side the Eagle might belong.

There were many birds about the cliffs and the rock chimneys, and all day high in the air flocks of birds had been circling, black against the pale sky. As they lay in their camp that day Aragon watched the flights doubtfully, wondering if Gollum had been doing some mischief and the news of their voyage was now moving in the wilderness. Later as the sun was setting, and the Company was stirring and getting ready to start again, he described a dark spot against a fading light: a great bird high and far off, now wheeling, now flying on slowly southwards.

"What is that, Legolas?" he asked, pointing to the northern sky. "Is it, I think, an eagle?"

"Yes," said Legolas. "It is an eagle, a hunting eagle. I wonder what that forebodes. It is far from the mountains."

"The Great River," The Fellowship of the Ring

Both of them are suspicious of seeing an Eagle so far from its natural habitat. They are also paranoid about Gollum's mischief and they know that the far side of the River Anduin is crawling with orcs and goblins.

3. The One Ring would lose itself if in custody of the Eagles

One of the abilities of the One Ring is to find itself a new possessor. It has a habit of losing itself when it becomes tired or bored of its current possessor.

Giving the One Ring to the Eagles is risky for a couple of reasons. First, as mentioned earlier, the Eagles would not truly understand the need to destroy the One Ring, so the One Ring can use that to slip away from the Eagles as they will not pay much attention to it. Second, the One Ring could use its influence to persuade them to drop it somewhere else. The Eagles would probably not care which volcano they dropped it into.

Dropping the One Ring in the wilderness means there's a high probability that the One Ring could be found by one of Sauron's many, many flying spies, many of whom would be attracted to a shiny bauble like the One Ring. From there, it's easy to fly the One Ring back to Mordor to its Master's hand.

4. The One Ring could exert a more dangerous power over the Eagles

The Great Eagles are creatures of tremendous power. Gwaihir the Wind Lord is the mightiest of them all, wise and powerful beyond all other flying creatures.

For him, the One Ring is even more dangerous, as explained by Elrond:

"Its strength, Boromir, is too great for anyone to wield at will, save only those who have a great power of their own. But for them it holds an even deadlier peril. The very desire of it corrupts the heart. Consider Saruman. If any of the Wise should with this Ring overthrow the Lord of Mordor, using his own arts, he would then set himself on Sauron's throne, and yet another Dark Lord would appear."

"The Council of Elrond," The Fellowship of the Ring

Elrond's point is made crystal clear when Frodo offers to give the One Ring to Galadriel. She very nearly succumbs to temptation, but recognizes the test for what it is, and is able to resist the desire to claim the One Ring for herself. If the One Ring can nearly seduce the wisest being in Middle-Earth in the very heart of her domain, her seat of power, what might it do to an Eagle, a creature that is basically defined by the word "pride?"

Any Eagle that possessed the One Ring runs the very real risk of being seduced by the power it offers.

The power of the One Ring is quite subtle and widespread. Saruman never came within a hundred miles of the One Ring and yet he was seduced by it simply by knowing its lore. Although his interactions with Sauron through the palantir probably didn't help.

5. The role of prophecy and destiny

The fate of the One Ring was tied up with multiple destinies. Frodo's is the most obvious, but Sam, Gollum, Aragorn, and even Gandalf all had their own fates woven into the fate of the One Ring.

Both Aragorn and Gandalf had to experience their own hero's journey during this adventure.

Gandalf the Grey was fated to die and be reborn as Mithrandir, or Gandalf the White, to replace Saruman as the leader of the Wise.

Aragorn's destiny was to return to Gondor to claim his birthright, but before that time he had to establish that he was worthy of being the king that Gondor needed. "The hands of the king are the hands of a healer." (The Return of the King) Aragorn had to develop his own strengths and demonstrate his leadership potential through his actions across Rohan and Gondor. In order to accomplish that task, he needed the time afforded to him by the journey of the One Ring towards Mount Doom.

Gollum's fate was sealed when he attempted to snatch the One Ring from Frodo. At that point, Frodo wielded the influence of the One Ring against another creature, thus sealing his own doom and failing the Quest.

"Down, down!" he [Frodo] gasped, clutching his hand to his breast, so that beneath the cover of the leather shirt he clasped the Ring. "Down, you creeping thing, and out of my path! Your time is at an end. You cannot betray me or slay me now."

Then suddenly, as before under the eaves of the Emyn Muil, Sam saw these two rivals with other vision. A crouching shape, scarcely more than a shadow of a living thing, ruined and defeated, yet filled with a hideous lust and rage; and before it stood stern, untouchable now by pity, a figure robed in white, but at its breast it held a wheel of fire. Out of the fire spoke a commanding voice.

"Begone and trouble me no more! If you touch me ever again, you shall be cast yourself into the Fires of Doom."

"Mount Doom," The Return of the King

This is the moment when the Ring is truly destroyed, as Gollum was commanded by the Ringbearer to fulfil a task, and nothing in Middle-Earth, save perhaps Sauron himself, would be able to countermand that order.

Had the Ring been carried by an Eagle, none of this would have occurred, and Middle-Earth would be doomed.

Destroying the One Ring was not the task that was appointed to the Eagles. That task was for Elves, Men, Dwarves, and Hobbits. In an early chapter of The Fellowship of the Ring, Gandalf notes that there are far greater powers than he and Sauron that are moving in the world, and that Frodo's actions and decisions are being guided by such powers, whether he knows it or not.

"Beyond that there was something else at work, beyond any design of the Ring-maker. I can put it no plainer than by saying that Bilbo was meant to find the Ring, and not by its maker. In which case you were also meant to have it. And that may be an encouraging thought."

"The Shadow of the Past," The Fellowship of the Ring

Final question...if the Eagles couldn't fly the Ring to Mordor, then why were they able to fly in and rescue Frodo and Sam?

I leave that as an exercise for the reader, because that question is also answered directly in the text.