So since there’s that pesky thing called the square cube law, it’s pretty universally accepted that large dragons have no chance at actual flight. However, all is not lost for the concept of giant winged reptiles! At least so I hope.
So baby dragons would use their wings to fly, thus keeping their original purpose. However, as they get larger the wings, even if they were absolutely massive, would not be sufficient for actual flight, and would instead enable the dragon to glide, increase jump height, etc.
My question is what can truly massive dragons use their wings for? Think dragons the size of Smaug from the Hobbit movies or larger. These beasts have no chance at any kind of flight, and I don’t really see gliding as a great option either.
For some additional information, no magic is at work here, though I will accept the dragons being tougher and stronger than current biology would suggest. These dragons are different species, and live in a range of biomes, but for this question I will narrow it to a specific dragon I have in mind.
The Titan Dragon is massive, with lengths of up to two miles and weighing hundreds of tons. Their massive size was previously thought to be completely impossible for any terrestrial animal, but somehow the dragon still grows to such an incredible scale. Most of its time is spent asleep, absorbing nutrients from the air, water, soil, and stone around it. When it is awake, however, it is immensely powerful and dangerous, with a breath attack that is either a massive flaming blast, or an equally powerful blast of supercooled gas. Their wingspan is often larger than the length of their body, however they are completely incapable of flight.