There are two news events that come to mind. One Saturday morning, in the middle of a pledge drive, I realized that Scott Simon had "broken format," as we say, meaning that he was ignoring the normal clock and blowing through breaks. We learned that the space shuttle Columbia had burned up during re-entry. We immediately ceased fundraising, jumped on AP, and regrouped. We pre-empted the rest of the day's programming to stick with NPR's special coverage of the disaster.
And of course, another major news event was 9/11. I was on the air that morning and I'll never forget hearing first about Tower One, then Tower Two, the Pentagon, the plane in Pennsylvania...all programming other than NPR's ceased, and we sent our reporters into the field to cover the story. Our music department also put together a very moving sequence of classical pieces to help listeners deal with the events of the day.