Electric? Nitro? If electric just turn the motor and use two other holes?
In any case the only solution is to re-tap the holes. If you don't own a tap and die set I believe Dubro sells them in singles and your local hobby store should have them.
As advice, if you've never re-tapped before practice on a scrap piece of aluminum and get the hang of it (you'll need a drill with matching bit size). Make sure you use cutting oil, work slowly, and keep the tap straight.
Good luck.