Flight Information:
As you may have noticed already dragons can fly (no, really? :P). Each color of dragon is a different size wingspan, but there are averages for each.
Silver: 100 feet
Blue: 90 feet
Bronze: 80 feet
Gold: 60-70 feet
White: 53 feet
Green: 47 feet
Purple: 25 feet
But some are, as I said, way different than the averages. The only dragons that may not be able to fly with rider would be purples, if they are under 15 feet wingspan. Also, they have a certain limit to how far they can fly. Usually, the larger can fly the longest, and the smaller the least. Larger dragons can fly for very long periods of time, up to half the way around the planet at once. (What also helps is the formation of flights. See Flight Formations). Their wings are similar in shape to a bat's wing. They have a permanently bent arm (on the wing) for stability and shock-reduction. The wing fabric on the wingsails is somewhat elastic, and thicker near the bones. They have a flap in front of the wing-arm that maintains the airfoil shape (which is needed to keep the air flow going faster underneath for lift). The tail of the dragon acts as a rudder, and the wings can be tilted as wholes to produce the ailerons.