Concern of a bomber gap grew after the 1955 Soviet Aviation Day and the Soviets rejected the "Open Skies" Treaty proposed at the Geneva Summit on 21 July 1955. US bomber strength peaked with "over 2,500 bombers" after production "of over 2,000 B-47s and almost 750 B-52s" (circa 1956, 50% of SAC aircraft &amp; 80% of SAC bombers were B-47s).