In The Legend of Zelda: Skyward Sword when trying to race on the bird, I only seem to lose altitude. How can I fly up?!
It's because you're not going fast enough while going upwards and therefor stalling (which causes you to lose lift).
You can flick your Wii remote to flap your wings and fly upwards.
I figured it out, you have to swing the Wiimote side to side multiple times. Its just like a horizontal sword swing.