The event that nearly ended the Apollo Program.
"Each January NASA pauses to honour members of the NASA family who lost their lives while furthering the cause of exploration and discovery, including the crews of Apollo 1 and space shuttles Challenger and Columbia. In 2022, the Day of Remembrance is observed on Jan. 27. This year’s NASA Day of Remembrance also marks 55 years since the Apollo 1 tragedy. "
https://www.nasa.gov/feature/55-year...the-launch-pad