This question is usually asked in relation to the debate about the wings of Balrogs, and specifically
whether those wings existed at all. For some background on this topic, see the main Encyclopedia's entry for Balrogs.
One of the main objections to the Balrogs' possession of wings is the fact that they tend to behave in a
extremely flightless manner. There are three known cases of Balrogs falling great distances - fatally,
in two of these cases. This is presented as part of the argument against their having wings, in that we wouldn't expect a creature
equipped with wings to plummet to its death quite so frequently.
A common counterargument to this is that it assumes that a winged Balrog must necessarily be able to fly.
It ignores the possibility that the Balrog had wings, but couldn't use them. This allows for the
Balrog to display its wings to the Fellowship at the
Bridge of Khazad-dûm, while explaining, for example, why it couldn't use them when it
fell into a chasm moments later. Those who take this position often back up their counterargument by pointing out that there are
numerous kinds of birds that are both winged and flightless. If, say, a penguin were to fall into a deep chasm, it could not fly out
again, but we would not be justified in assuming from this that it didn't have wings.
When we consider the implications of this position, it seems rather difficult to sustain. We can understand why certain
birds are flightless because of their evolutionary ancestry. Penguins can't fly because their ancestors found their wings more
useful for swimming; ostriches can't fly because their ancestors grew too large to use their wings; dodos couldn't fly
because their ancestors just didn't need to bother. These are gross simplifications, of course, but they illustrate the point -
winged flightless birds have their wings because somewhere in their ancestry was a creature that could fly. In other words,
wings do imply flight, though that ability might have been lost at some point.
None of this applies to Balrogs. A Balrog's ancestors couldn't lose the
power of flight, because it had no ancestors. Whether or not it had wings would probably have been its own choice, or at least that
of its creator. For the 'flightless Balrog' idea to hold, we'd have to assume that the
Balrog possessed a huge pair of unusable wings as the result of a deliberate decision.
It hardly seems plausible that the Balrog, having decided on the form of a monstrous winged
fire-demon, and given the choice of being able to fly or not, would choose 'not'.
It's only fair to point out that this doesn't actually disprove the flightless Balrog hypothesis, but it
makes it rather difficult to support. To take the idea to extremes, we might perhaps construct a scenario where the
Balrogs started out as flying creatures, but lost the ability in some unknown way, or where
Balrogs actually can fly, but choose not to. There isn't a shred of evidence
for any of this, though. Where a position requires this degree of inventiveness to hold it up, its usefulness becomes
Its hard to believe that Tolkien intended any of these bizarre scenarios, and even harder to believe that, if he had,
he would have failed to mention them. Is it possible that Balrogs had wings, but couldn't fly? Well,
it's not impossible, but it seems very, very unlikely.