We know that in order for modern flight to take place, countless thousands of man-hours and much high technology had to go into the design process. It just doesn't fit. It's obvious that these creatures have not come about by chance and selection, but have in fact been designed. You find that those creatures which are flying now and are also fossilized in the rocks were essentially the same then as they are now. There is no sign at all of any gradual evolutionary change.
Butterflies are exactly the same in the fossil record.
When it comes to birds, they're essentially, structure-wise, the same. And bats are exactly the same in the fossil record as they are today. The feather is made such that if you bend it, everything bends with it, and yet it's a very light structure. But if you have a sliding joint, you need lubrication. To do this the bird twists its neck around 180 and dips its beak into a tiny oil gland right down at the back of its spine.