If you keep the disc on the wheel, ziptied to the frame, grab a block of styrofoam, cut appropriately into two sections trimmed to fit around the hub bolts, press it onto the disc and secure it. on asian flights, we can fill the box with gear, so this prevents stuff in the box from damaging the disc.

If you remove it, tape it to a thick square of cardboard first, then put it in a ziploc.