The idea of the Eagles transporting the Ring to Mount Doom, or at least part of the way, is not discussed in The Lord of the Rings and Tolkien himself apparently never specifically addressed it, except in an oblique manner. In The Letters of J. R. R. Tolkien, he stated: "The Eagles are a dangerous 'machine'. I have used them sparingly, and that is the absolute limit of their credibility or usefulness. The alighting of a Great Eagle of the Misty Mountains in the Shire is absurd; it also makes the later capture of G. [Gandalf] by Saruman incredible, and spoils the account of his escape." (Letter 210) In the DVD commentary for Peter Jackson's film adaptation of The Return of the King, Jackson and Fran Walsh joke that not using the Eagles to travel directly to Mount Doom was a plot hole, at which point Philippa Boyens angrily points out to them that the Flying Nazgûl would have intercepted them had they attempted this, and it simply became a common joke that it was a plot hole because the Flying Nazgûl were not introduced in the first film, a point to which Jackson and Walsh humbly conceded.
