I have this one - the Wheel Away Pet Carrier
http://www.snoozer-dog-beds.com/WheelAway/wheel1.htm
It is a backpack or has wheels and a telescoping handle to convert to a rolling bag. It is airline approved. I haven't used it yet as a backpack - but it works really nicely as a rolling bag.
It comes in different sizes and I found it at Petco as well as several places online.