Picture shows P-51 mustangs (the Cadillac of the skies) in formation, flying cover for B-17s on a bomb run over Europe .. The P51 Mustang was one of the most effective planes of World War Two. The P51 Mustang gave the bombers of US 8th Air Force the fighter cover it so desperately needed over occupied Europe and, therefore, greatly assisted the bombing campaign against Germany in World War Two. In May 1944, the P51-D was introduced. This plane was fitted with fuel drop tanks that gave it far greater mileage in the air. When these tanks were empty, they could be dropped so that the plane had the full use of its aerodynamics. This extra fuel gave the Mustang an ability to escort the US 8th Air Force bomber formations to just about any target in Western Europe. Such cover was vital to the Americans as they were participating in daylight raids primarily over Germany and were thus exposed to attacks by the Luftwaffe. Before the Mustang, American bombers flew in a box formation and relied on the fire power of the many guns carried by Flying Fortresses to protect a formation. Now the B17's had a fighter escort to enhance this fire power. The Mustangs speed and manoeuvrability in the air made it a severe test for the Luftwaffe's fighter pilots.