B-52 and B-2

A B-52 flies side-by-side with the (relatively speaking) new kid on the block, the B-2 Spirit bomber, which was unveiled to the public in 1988 but which didn't really go into service until well into the 1990s. Over the decades, Boeing built more than 740 of the B-52 aircraft, the last one way back in 1962. By contrast, the U.S. Air Force has an inventory of only about 20 B-2s.

Here's another significant statistic: According to an excellent story in Wired's Danger Room blog recounting the history of U.S. long-range bombers, the cost of an individual B-52 ran to about $70 million (in today's dollars), while the B-2 carried an "eye-watering $3-billion-a-pop unit price."

And get this: the Air Force says the life span of the B-52 could extend to 2040 and beyond, and it's got the engineering analyses to prove it.