Training Wings
Run into Falcon on the upper levels of Attilan.
This fight is the style of the Vulture fights- projectile weapons do nothing, just catch up to him and start punching.
Falcon has a fair amount of health, so this can take a while. Also, like Green Goblin 2099, he sometimes leaves explosives in his wake, so you may be better off skipping the speedwarps entirely. Instead, noting the Falcon just keeps making the same loops, cut him off as he turns or corners on his route.
Smack him down a sufficient number of times to unlock him for purchase.
