The U.S. space agency NASA has marked the 25th anniversary of the space shuttle Challenger disaster, which killed all seven crew members and triggered questions about the safety of shuttle flights.
The crew was honored Friday in a ceremony at Kennedy Space Center in Florida.
Speakers included June Scobee Rodgers, widow of Challenger commander Dick Scobee. She said, like everyone watching around the world, family members and colleagues of the crew were stunned to see an "unspeakable" tragedy "unfold right before our very own eyes."
On January 28, 1986, the Challenger exploded 73 seconds after blasting off from the Kennedy Space Center. The explosion was found to be linked to faulty seals on the launch vehicle.
One crew member was school teacher Christa McAuliffe. She was the first teacher being sent into space as part of a NASA program, and many school children around the country were watching the event live.
The Challenger crew included an African-American, a Japanese-American and two women, one of whom was Jewish.
June Scobee Rogers and others spoke at the ceremony in front of a memorial inscribed with the names of the seven Challenger crew members and others who have perished as part of U.S. space missions.
On Thursday, NASA observed its annual Day of Remembrance ceremonies at the Kennedy Space Center and Arlington National Cemetery outside Washington.
In addition to the crew of Challenger, the day was set aside to pay tribute to the three-man crew of Apollo 1, and the seven-man crew of the space shuttle Columbia. The Apollo 1 crew was killed in a flash fire inside the spacecraft on January 27,1967. The Columbia crew perished when the shuttle disintegrated while re-entering Earth's atmosphere on February 1, 2003.
Two of the Challenger crew members are buried at Arlington Cemetery. Shrines for the Challenger and Columbia crews are also erected at the cemetery.
Some information for this report was provided by AP, AFP and Reuters.