Meanwhile, the strength of the US and British bomber fleets had increased. Based in Britain, they began operations against German targets. The first thousand-bomber raid was staged on Cologne on 30 May 1942. Air raids continued on targets farther from England after auxiliary fuel tanks were installed on US fighter aircraft. Göring refused to believe reports that American fighters had been shot down as far east as Aachen in winter 1942–1943. His reputation began to decline.