I don't fly that often but one of the times I flew I had on plastic bloomers that went down almost to my knees and when I walked through the body scanner it showed up because It showed something unusual on my legs triggering a pat down and I explained what it was and they sent me through without issue after they seen visually what it was. But I fly diapered all the time with diapers in my carry on and have never had a problem as a result.