Can't shoot through glass on hovercraft

yep there is some trick to it because people get shot out of the hovercraft routinely.  I've been shot out a few times.  

It might be easier  to shoot the gunner than the driver. And/or possibly shooting in the side window is easier.  Maybe it's a really straight (perpendicular)  shot through the front glass.  

I haven't spent enough time on it yet.  And haven't googled it yet either.