In the Fly skill, it says:
"You cannot take this skill without a natural means of flight or gliding. Creatures can also take ranks in Fly if they possess a reliable means of flying every day (either through a spell or other magical manner, such as a druid’s wild shape ability)."
Since you must have a natural means of flight to have the skill and Garuda-Blooded Aasimar automatically get this as a skill, (in my head) that means Garuda-Blooded Aasimar have usable wings. This may be me wanting things for free.