Um, aircraft didn't actually explode all that much when hit with fighter guns. Except when they caught on fire, burned abit, and then went *BOOM*
Aircraft in AHII DO go boom when you hit the pilot. Does your idea mean that if I put a single round through the head of the enemy a/c's pilot, at 150 yards, I would be killed by the resulting explosion. When in the reality the thing would have just flown itself all the way to ground impact?
BTW, if you intend this as a anti-vulching measure, there are better ones. More and better field guns, for instance.