The Great Eagle Mystery

Perhaps the Eagles did not aid the Fellowship in their quest to destroy the ring by simply flying them to Mordor because the plight of the ring was for the free peoples of Middle Earth to accomplish. The Eagles, although mortal, were considered the messengers and servants of Manwe and were allowed to aid the peoples of Middle Earth in times of need, but maybe not with this specific quest....who knows.

I believe they could make the trip, as Eagles did nest in the highest peaks of the Misty Mountains in the third age, and could fly great distances and easily carry a man. However I agree that the clouds of ash and the summoned elements of weather would be a deterrent to them. But I do think a squad of Eagles would easily handle the Nazgul and their flying steeds. After all, the Eagles do have a solid history of combat and taking care of business. Remember, these were the creatures that fought and destroyed Ancalagon and his brood in the War of Wrath. Even if the Eagles of the Third Age were one-third the size of their kin from the First Age, they would still have a wingspan of roughly 50 feet along with talons, beaks, brains, and the ability to fight as a team in battle. My money would be on the Eagles of Manwe over the slow-witted Nazgul-gang any day.