[The Might]

What just came to mind whilst reading the last posts, is that the general vulnerability of dragons seems to play the decisive role in giving balrogs the upper hand in a battle.

Now, balrogs too are vulnerable, but usually it appears that it takes quite a lot to kill them. Never is a balrog killed with a sword, or an axe, or an arrow (at least not that I am aware of, and I am not taking early BoLT texts into account where they are much weaker). They always fall to their deaths - Gothmog, Glorfindel's balrog and the one in Moria all fall to their deaths.

Now dragons on the other hand don't need to fall from so high, you jsutn eed to find their weak spot - their underbelly. Glaurung died because of it, Smaug also, and I daresay that this is a very likely way of how Earendil defeated Ancalagon.

So the question is - how could Ancalagon catch Gothmog and drop him from high above without getting a big axe stuck in his underbelly? I personally don't see that happening easily, especially with the trusty whip with which Gothmog could hold on well.