Two reasons the B-52s are still around -<p>1) its replacements, even if they had worked perfectly, would not have improved upon the original to a degree not already covered by ICBMs, cruise missiles, and drones. It fills its niche perfectly, as does its Russian counterpart.<p>2) its three toughest opponents have been Vietnam, Iraq, and Serbia. Scrappy countries to be sure, but not first-class air defenses with targets deep in enemy territory. So very few have been shot down.<p>I suppose once the parts run out to keep a decent fleet operational, we should consider building exact duplicates - with some modern upgrades of course, and just keep trucking.