At 100,000 ft.the thin air offered considerably less resistance to the shot and pattern than 2500 ft. The remedy is to open up the choke. When I would travel to Florida to shoot from Arizona I found I had to tighten my choke and pattern to compensate for the lower altitude and extremely humid air compared to Arizona. In that case it wouldn't be much, but when shooting all those registered targets you notice the difference. In Colorado I had already left by the time I realized what the problem was, so have no idea how much I would have had to open the choke.
