I received this hoary query ...

And this was what the letter said:

I read that you were a Tolkien scholar so I was hoping you might be able to answer a question regarding the LOTR story. It has been asked why the one of the Eagles couldn't take Frodo to Mt. Doom in the first place, but no one seems to be able to answer this. I'm having a hard time finding anyone who will even take this question seriously; they all give the same lame copout answers ("because then there would be no story; eagles weren't taxis, etc.). My belief is that this was a hole in the plot that Tolkien failed to address. One might imagine that there were reasons not given in the story which would rule out the Eagles plan, but to be honest I'm not sure if there would be any way to explain it without making a couple minor revisions to the story. Even so I think it would be a difficult problem to solve. Tolkien himself admitted that the Eagles were "a dangerous literary tool". I was just wondering if you'd heard any discussion on this and if you had any thoughts on the subject. Any insight you could give me would be greatly appreciated.

( And this was my reply )