It’s not exactly a whimsical or inspirational story, because basically things go wrong for him the whole time while being gradually shunned from society. And then he runs away. It’s hard to see the denouement as anything but bittersweet. You’d really need to do the whole movie in a very fanciful, unrealistic manner in order to be enjoyable.
It’s difficult to come up with a title because I can’t visualize the style.
They All Laughed
The Thing With Feathers
Grounded
How about just Glider? Or Glide? Kind of alludes to him being above or set apart from everyone else, and being carried along by greater forces, while at the same time trying to control his course.
Eretico In Volo … Bonus points for sounding enough like a Rocco Siffredi flick to appeal to a wider audience 
Up
Codex on the Flight of Birds.
From this.
I dunno, just sounds like the right level of indy-quirky to me, I guess.
Airborne?
Air Born?
I’d rename him Leonardo and call it Leonardo da Whatevertown.
One Day I’ll Fly Away.
Flights of Fancy.
Matt Damon in Air Bourne
Mr. Blue Sky
Volare
Zen and the Art of Gliding
No flies on me
Flies undone
Best idea so far.
Got a theme song ready!
Deus Ex Machina (Latin for “God From The Machine”), which could/would be a good sub-plot regarding how the populace thinks of this invention.
This is also a phrase used in story telling to get a character out of a tight situation, at the last moment, to basically create a happy end out of thin air - which sounds appropriate for your screenplay.
On the same note M****achina Ex Deus would also work
.
When he takes off in the final scene of the movie, what if the glider is hit by a solar flare and he is somehow transported to The Bronx, New York in 1983?
That sets the stage for the big sequel: Glidin’ 2: Electric Boogaloo
Gilbert is found by a break dancing crew in The Bronx. Gilbert’s initial awkward attempts at fitting in with the crew create a lot of comedy hijinks. Ultimately, Gilbert is accepted by the crew and his showstopping glider stunts make his crew the undisputed break dancing champions.
Whaddya say?
It’ll never fly.
I liked yours- I’ll send you a check if I ever write a book.