Some of you guys are making a mistake in your math on this.
For bomber pilots, kills / (bombers lost) is not 3 * K/D but at most 1/3 * K/D because K/loss = K/D * D/loss, and D/loss is at most 1/3 (i.e., one D per 3 losses). I say "at most" because there are times when there is no death, but one or two bombers were shot down. Thus D/loss is even smaller than 1/3.
For B-17's, if average K/D is 0.33, then average K/(bomber lost) is less than 0.11.