For examples in planned economies, USSR had a lot of examples, and this article is another. For examples in otherwise-freemarket-but-not-in-this-case economies, see "too big to fail" situation with bank bailouts, and your own example on USA military industrial complex - where failed projects get propped up instead of allowing them to die as they should, thus in the end harming the long-run perspective in the whole sector.
With hindsight it would have been better for the industry to decline gradually than laying off everyone at once.
Look at a large corporation like IBM some floundering business units persist for decades because of the internal political cost of ending them when economically it is the prudent thing to do.