Joining the Wonderbolts isn't as fast or simple as Rainbow Dash imagines. Soarin thinks about his own mentor, Dusty Roads, as he helps the new recruit see whether she has what it takes -- and whether joining is really what she wants.
(Inspired by the comic "Memories", the cover image's nonchalant pose, and the story "Moonspire Run" by TitanRising. In hindsight I should've asked TR for permission to imply that their story is considered canon in this one.)