I never thought of that, but I have often played a few balls with the glass off after doing a repair to make sure everything is working. I've never had an issue despite having lots of air balls during actual games with the glass on. I believe all my air balls were heading in my direction or to the side and not to the back glass. Still, anything can happen I suppose. Case in point: Today, while driving on the highway, a semi truck in front of me lost a spare tire and some part from it came flying through the air only to find the hood of my new(ish) car. It could have been much worse, for me and the people in back of me. Luckily, there was only a slight dent and scratch. Still, if I had gotten there a split second earlier, it probably would have gone through the windshield, and if I had gotten there a split second later, it would have missed me entirely. All that said, I think you will probably be fine playing with the glass off.

Has anyone ever had an air ball shatter the playfield glass? Sometimes I worry that that might happen with how hard some of my balls bounce off of the glass.