Tactics: Skykine only willingly attack creatures much smaller than themselves, fleeing if faced with a larger opponent (or even a smaller one, if it's aggressive enough), all the while emitting loud barks to warn their herd of the danger.
I'd rather quote a particular size or size-relationship.
A skykine may try to eat any flying creature less than half its own size. Larger opponents (or smaller ones who prove dangerous) prompt a skykine to flee toward its herd while barking in alarm. The skykine normally only stops and fights if it is unable to escape from pursuers who have injured or beleaguered it. However, bulls defending their mates, or adults defending their family's young, will initiate combat, and mother skykine willingly fight to the death to defend their offspring.
Hmm, you know there's not much in the way of actual tactics there - shouldn't most of this be in background information?
Do we need a weight too? They seem to be shaped roughly like a whale, and are the same length as a Right Whale (which are up to 65 feet / 100 tons), so we could use those figures.
100 tons seems too heavy, though, and flying creatures are almost always lighter than swimmers. Let's just halve it for the sake of argument.
How about:
A bulky dragon-shaped creature the color of the sky. Its batlike wings and four spindly legs are small and spindly, looking far too weak to support its whale-sized body. The beast's large head is as broad as its body, with long crocodilian jaws. A pair of globular eyes jut from opposite sides of a skull who's sloping forehead is far too flat to house much in the way of a brain.
Skykine are whale-sized flying creatures who spend their lives in the air, save for the brief periods the female skykine need to land to give live birth to their young. They are normally encountered in families or herds led by a single adult male – although that's nigh impossible to tell, since both bull and cow skykine appear identical to other species. Skykine hide is abrasively rough while being supple and tough, much like shagreen. Its color matches the sky – from azure blue to storm grey and cloud white.
Skykine are carnivorous but cowardly. They only eat flying creatures less than half their own size; but unfortunately are dull-witted enough to occasionally mistake small aerial vehicles for food. Encounters with larger predators, or supposed "prey" who prove dangerous, prompt a skykine to flee toward its herd while barking in alarm. The fleeing skykine normally only stops and fights if it is injured or beleaguered by pursuers it is unable to escape. However, bull skykine defending their mates, or adults defending their family's young, will initiate combat, and mother skykine willingly fight to the death to defend their offspring.
A skykine is 60 to 70 feet long. Its levitation organ means it's effectively weightless, but its mass is about 50 tons.
Combat
A skykine is a timid combatant who is only willing to attack opponents of a smaller size category than itself. It will flee anything larger than this, or whenever it takes significant damage. Only a cornered skykine will fight to the death, or a skykine cow who is defending her calf. An attacking skykine normally starts by ramming an enemy or, if its opponent is much smaller than itself, by charging and making a bite attack. It then lashes out with bites and tail slaps until the skykine wins or decides to run away.