It ain't the Fellowship of the Eagle

Every once in a while somebody asks why Gandalf didn't just have the Eagles carry the Ring to Mount Doom.

Even if we ignore the fact that the Ring is a tool of corruption that entices its bearer--especially a powerful bearer--towards betrayal, and that therefore giving it to an Eagle would probably not be a good idea,
    AND the fact that the entirety of the plan to destroy the Ring relied on Sauron not finding out about it and a flight of giant Eagles is not exactly subtle,
        AND the fact that Mordor is a long way from Rivendell even if you do have wings,
            AND the fact that the Eagles are not Gandalf's personal taxi service,

we still have to consider

• Sauron's air force (flying dragons, fell winged beasts, Nazgul, some birds)

• Sauron's anti-aircraft artillery (the ancient Numenorians had aircraft; presumably they also built weapons that could shoot at aircraft, and I would assume Sauron might have kept a few in reserve just in case--beyond that, I'm sure Shelob could probably fling a web pretty high)

• Sauron's ability to control the weather itself (just try flying over the mountains in hurricane-strength winds, or finding your way to the landing zone in a country filled with volcanic smoke)

In short... ONE DOES NOT SIMPLY FLY INTO MORDOR.