Hey, I played your game!
It's a solid game with basic mechanics, and is fun for a while. However, eventually I found it quite boring... I was just going through hoop after hoop endlessly.
What this game needs are unique mechanics and obstacles, to give the player a sense of achievement when they go through a hoop. Put some enemies there to stop you, put some birds in the way, add turbulence, bad/good weather... or something to make it more engaging. Even something as small as moving the hoops around for a harder target.
Maybe the plane can go faster or slower due to an upgrade or obstacle? Maybe it can have a gun to fire at these obstacles? Nosedives, tailspins, barrel rolls... everything planes can do, experiment with it and put it in!