@Background Pony #0239  
That would be a great idea and background explanation for how Pegasui and even earth ponies can use magic if it weren’t for so many people going ape shit over it and all those other damn haters and neigh sayers.

RD  
“I am sick and tired of you Wonderbolts rejecting me every time I try to join! I am already the fastest, toughest and most AWESOME Pegasi there is! What else to I need to prove?”
 
S  
“Wonderbolts isn’t just about having smooth moves and performing air shows. We’re part of the Equestrian Air Force, the most Elite fliers AND fighters of the skies. You want to be one of the best you have to PROVE you can beat the best!”
 
RD  
“You… want me to fight you?”
 
S  
“Precisely.”
 
RD  
“Fine, if that’s what it takes!”
 
[She takes off and hovers in the air. Tendrils of energy starts swirling around Rainbow Dash, and the air simmered with power that glows all colors of the color spectrum]
 
S  
“Great light-show, Dashie, how did you learn that?”
 
RD  
“All ponies could do magic. Just because Pegasi and Earth Ponies can’t directly control it from birth like Unicorns doesn’t mean they can’t bring it out without training.”
 
S  
“Real nice. I take it your egghead of a friend Twilight helped you figured this out?”
 
RD  
“That’s right, now take this!”
 
[Rainbow fires, but suddenly a sphere of flames conjures Spitfire and deflects the rainbow-colored blast. Dash look on in awe as the fire sphere dissipates to reveal a smug, and unharmed Wonderbolts captain]
 
RD  
“Wha - how did you -?”
 
S  
“You ain’t the first and only one to figure out how to do magic like that.”
 
[Conjures fireball on her hooves]
 
S  
“And I ain’t called Spitfire just because it sounds cool!”
 
[Dash shrugs]
 
RD  
“Looks like Twilight was right about not judging books by its cover.”
 
[She puts on a confident pose in the air as her aura of energy pulsates with greater rhythm and life]
 
RD  
“But enough talk, let’s get this over with once and for all! I’m going to get my Wonderbolts membership or go down trying!”
 
S  
“Brave words for a filly.”
 
[Spitfire’s back crackled to life as her two feathered wings glowed with intense heat and light, enlarging into two flaming wings]
 
S  
“But you’ll have to get past me first before you put on that costume! And come Tartarus or high water, you’re not getting it without a one hay of a fight!”
 
[And thus, the greatest aerial clash in the millennia begins…]