What kind of plane is it? did you get it as a RTF? have you crashed the plane any? i found the crystals/receiver on my RTF planes to be rather weak, i don't want to say the electronics that came with my Begin Air/J3 Cub are junk but i found them to be very glitchy after a few rough landings/crashes.

I replaced the receiver, crystal and radio on my Parkflyers Begin-Air and it took care of the problem, in fact... the plane responded much better.

Worth a shot.