For the U.S. Army Air Forces, daylight bombing was normal based upon box formations for defence from fighters. Bombing was coordinated through a lead aircraft but although still nominally precision bombing (as opposed to the area bombing carried out by RAF Bomber Command) the result of bombing from high level was still spread over an area. Before the war on practice ranges, some USAAF crews were able to produce very accurate results, but over Europe with weather and German fighters and anti-aircraft guns and the limited training for new crews this level of accuracy was impossible to reproduce. The US defined the target area as being a radius circle around the target point - for the majority of USAAF attacks only about 20% of the bombs dropped struck in this area. The U.S. daytime bombing raids were more effective in reducing German defences by engaging the German Luftwaffe than destruction of the means of aircraft production.