THE AIR FORCE STORY CHAPTER 18 "BIG WEEK" SATURATION AIR OFFENSIVE 1944 24484

Formally known as Operation Argument, Big Week was planned as a series of attacks by allied strategic bombers flying from bases in England and Italy. It was intended to lay waste to the German aircraft production industry. The attack had almost no impact on the German aircraft factories and their production capabilities. The lasting impact of the Big Week was that the Luftwaffe’s aerial defense squadrons had been nearly neutralized by the new P-51 Mustang. Approximately 17% of the Luftwaffe’s trained defensive pilots were killed in a single week. Air superiority shifted to the Allies in February 1944, not because of destroyed factories, but because the Luftwaffe had a critical shortage of trained airmen.
http://ww2flyover.org/flyover-formations/big-week/

From February 20–25, 1944, as part of the European strategic bombing campaign, the United States Strategic Air Forces (USSTAF) launched Operation Argument, a series of missions against the Third Reich that became known as Big Week. The planners intended to lure the Luftwaffe into a decisive battle by launching massive attacks on the German aircraft industry. By defeating the Luftwaffe, the Allies would achieve air superiority and the invasion of Europe could proceed. The daylight bombing campaign was also supported by RAF Bomber Command, operating against the same targets at night. Arthur Harris resisted contributing RAF forces as it diverted them from the British area bombing offensive. It took a direct order from Air Chief Marshal Sir Charles Portal, Chief of the Air Staff to force Harris to comply. RAF Fighter Command also provided escort for USAAF bomber formations, just at the time that the Eighth Air Force had started introducing the P-51 long-range fighter to take over the role.
https://en.wikipedia.org/wiki/Big_Week