“Ladies and gentlemen, I'd planned to speak to you tonight to report on the state of the Union,” began President Ronald Reagan in a televised speech from the Oval Office. “But the events of earlier today have led me to change those plans. Today is a day for mourning and remembering.”

It was January 28, 1986, the day the space shuttle orbiter Challenger exploded in the sky, killing all seven astronauts on board. Out of respect, Reagan and his aides decided to postpone the state of the Union speech he was supposed to give that evening until the next week—marking the first time a president had ever delayed the yearly address.

Reagan was in the Oval Office at 11:44 A.M. that day when Pat Buchanan, then the president’s director of communications, walked in and said: “Sir, the shuttle blew up.” Reagan asked if the Challenger was the one carrying a teacher; though he must have already known the answer, since he was planning to mention her in his state of the Union speech that evening. That particular addition to the crew had been his idea. During his 1984 reelection campaign, Reagan had launched the Teacher in Space Project that selected Christa McAuliffe from among some 10,000 applicants.

“Reagan had a pretty strong populist streak,” says Russell Riley, co-chair of the Presidential Oral History Program at the University of Virginia’s Miller Center. Riley specuates the president may have wanted to put a teacher in space to draw positive attention to the space program and make people feel like they, as regular citizens, were connected to it.

McAuliffe was one of two women aboard the Challenger, and she was poised to become the first “ordinary citizen” in space, The New York Times reported. When Reagan heard that her spacecraft had exploded, “His eyes went wide, his mouth opened in total surprise,” recounted Alfred Kingon, Reagan’s Cabinet secretary, to the Times. The president and his aides huddled around a television and watched footage of the explosion in silence for several minutes. Reagan later recalled it as “a very traumatic experience.”

“I certainly remember that it was a shocking incident, a stunning incident,” Riley says. “There had grown a sense of complacency about the space program among people who were on the outside; that we had had such great successes and everything had gone really well for an extended period of time.”

The Challenger disaster, he says, “punctured this image of routine.”

The president and his aides decided that he shouldn’t deliver his state of the Union speech that night. Instead, at 5:00 P.M., Reagan gave a televised address from his Oval Office about the disaster. In his speech, he addressed the sense of complacency Riley mentions.

“We've grown used to wonders in this century,” Reagan said. “It's hard to dazzle us. But for 25 years the United States space program has been doing just that. We've grown used to the idea of space, and perhaps we forget that we've only just begun. We're still pioneers. They, the members of the Challenger crew, were pioneers.”

Reagan concluded by quoting a poem by John Gillespie Magee, an American airman who died in World War II when he was only 19.

“We will never forget them,” he said, “nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and ‘slipped the surly bonds of earth’ to ‘touch the face of God.’”