In 2003, the space shuttle Columbia was lost when an accident at launch - noticed but not acted upon - conspired to destroy it upon re-entry. It was a great tragedy, and one that spurred NASA to develop a contingency plan, which could have saved the stricken crew. It reads like a movie script that would make Apollo 13 look like a kids movie.
The Columbia's demise was put down to a busted tile on the shuttle's wing, which failed to protect the ship from the intense heat generated by returning to the earth's atmosphere from space. That tile was broken during launch.
The resulting inquiry into the Columbia explosion resulted in NASA being asked to come up with a hypothetical rescue plan that might have saved the ship. It obviously never had the chance again to put the plan into motion, but boy, if it had been, it would have been one hell of a thing.
Ars Technica has a fantastic run-through of the plan, which would have involved rushing the Atlantis through pre-flight, getting it into orbit then transferring the crew.
Sounds easy on paper, but it would have required the entire ground team to work around-the-clock shifts for weeks. And if a single pre-flight check had failed, the mission would have been lost, because Columbia only had a finite time its crew could survive in space.
It's a very long read, but it's very much worth it.