Well, I could and I'm at the Pokemon League.
My only guess is that you haven't made it to Route 121 or Lilycove.
You are unable to fly to routes if you haven't made it to the town (or route, possibly, in this case) after it. This is proven on Route 121, coincidentally the route after this one; there is a woman that states you have to make it to Lilycove in order to fly to Route 121.
If you have made it to Route 121/Lilycove, I guess its a glitch. Sorry...
Hope I helped. :)