You grab some helmet out of one of the boxes and head up to show it to Uncle Jack.
As you arrive and he sees the helmet he smiles, "Ahh you wanna be a fly boy". You shrug and place the helmet next to you as you sit down on the table. As you both eat Uncle Jack suggests, "We can try out that helmet once we've eaten, I think it's one of my better works". Judging by your unenthusiastic reaction he continues, "You still don't believe me, do you?".
As you finished eating you sigh, get up and put up that stupid helmet. Curiously Uncle Jack watches you eagerly. Just moments after you put on the slightly oversized helmet, you notice that it seems to get tighter. At the same time you notice that you seem to get shorter. As you feel things poking from inside your clothes you get spooked off and instinctively pull off your clothes just before they get ripped. Looking back you notice a set of jet fighter wings growing, complete with engines. Suddenly you notice your legs having shrunken down comically, basically keeping your former crotch just inches away from the ground. Looking down you notice your penis retracting and forming a cap. Apart from that cap your crotch seems to be made out of black corrugated rubber extending backwards past your bum. It's hard to make out, as the wings on your back block your view, but there seem to be a set of flight control surfaces like on the tail of a jet fighter.
Within moments your avionics kick in and you find yourself having new momentarily confusing senses. Not only can you sense how full your new fuel tank is, but you gain a new new sense of where down is or where you are. Meanwhile your front has changed too, two box like growth, air intakes to your engines have formed on the sides of your chest going down to your belly. On your chest a sort of oversized breathing mask pushes itself into existence connected to the rest of you via a pair of hoses. You notice that you can radar ping your environment from it, even if it's just hanging there.
Confused to try to waddle on your short legs in a circle to see your back, but then Uncle Jack pulls out a video camera with radio transmitter and turns it on. Instantly you notice the new radio source and tune it in to get an outside picture of yourself.
You look like a fairly stubby cross between a toy robot and a jet plane. Much shorter and smaller as they typically are and painted in camouflage. Your tail contains a set of stabilizers with the vertical ones almost towering over your head. On your back you can see your main wings as well as your engines. While you feel certainly more stiffer than before, you find that you could stretch out so your bum so you'd be straight to glide in the air. One thing you notice is that you now are more compact, only about 5 feet high, but about as long and depending on how you position your flight surfaces, between 3 and 6 feet wide. An almost comically short jet fighter.
You ask Jack "What am I?" He replies, "Well what do you think you are?". Confusedly you query your avionics system, "I think I'm some sort of jet plane... I think I can even fly...". Jack explains, "Yeah, not very efficient, but up high enough you could certainly break the sound barrier."