I've always done a hot water bath - scared of the pressure cooker.
I did a few peaches last year in pints. This year I decided to do more peaches in quarts. When I pulled a couple of jars out of the water path, I thought they were "spitting". Now (I don't know if it's the same jars), There are several jars with air in them. Is that ok?
Did it happen if I filled the jars too full? or didn't get enough air out when I put in the syrup?
I generally freeze stuff, and when I've canned, it's jam or tomato juice - so I'm not sure about having fruit with air space under the seal.
Do you mean you have air bubbles in the liquid? Sometimes you can tip the jars to release the bubbles into the headspace. Did you run a knife or thin spatula down the sides of the jars before putting your lids on? That will release a lot of excess air before processing.