Thursday marks the 35th anniversary of the space shuttle Challenger disaster and serves as NASA’s annual day of remembrance to honor astronauts who died during missions.

“Hundreds of people in Florida and millions watching on live television witnessed the space shuttle Challenger break apart in a mid-air explosion on January 28, 1986, killing 7 people on board,” FOX 9 reported.

The disaster happened 73 seconds after the shuttle’s takeoff from the Kennedy Space Center in Cape Canaveral, Florida.

“The Challenger’s fuel tank collapsed, resulting in an explosion that killed the seven people on board and sent debris flying into the Atlantic Ocean,” the outlet said.

Those who lost their lives were Gregory Jarvis, Judith Resnik, Dick Scobee, Ronald McNair, Mike Smith, Ellison Onizuka, and Christa McAuliffe.

“On this Day of Remembrance, we honor the Challenger crew and all who gave their lives while furthering the cause of exploration and discovery,” NASA wrote online on Thursday:

Following the tragedy, President Ronald Reagan postponed his State of the Union address and delivered a televised eulogy to American citizens.

“We’ve never had a tragedy like this. And perhaps we’ve forgotten the courage it took for the crew of the shuttle. But they, the Challenger seven, were aware of the dangers and overcame them and did their jobs brilliantly,” he said.

Reagan continued:

We’ve grown used to wonders in this century. 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.

And I want to say something to the schoolchildren of America who were watching the live coverage of the shuttle’s takeoff. I know it’s hard to understand but sometimes painful things like this happen. It’s all part of the process of exploration and discovery. It’s all part of taking a chance and expanding man’s horizons.

“The future doesn’t belong to the faint-hearted. It belongs to the brave. The Challenger crew was pulling us into the future, and we’ll continue to follow them,” he stated.

NASA’s Kennedy Space Center live streamed a remembrance ceremony Thursday on its Facebook page: