The last time this happened it was during the first Gulf War two decades ago, so I got all giddy when I learned that someone actually had to shout "stop the presses" last night at the New York Times.
This is what happened, according to their Vice President of Corporate Communications, Eileen Murphy:
The news broke really late, and by that time we were already in the middle of the printing run. There was some discussion and because of the magnitude of the news, the order was given to stop the presses. It's been a long time since anyone can remember a run being stopped, papers being thrown out, and then a new run starting up.