Today marks the 25th anniversary of the space shuttle Challenger NASA commemorates.
(L to R): Mission Specialist, Ellison S. Onizuka, Teacher in Space Participant Sharon Christa McAuliffe, Payload Specialist, Greg Jarvis and Mission Specialist, Judy Resnik. Front row (L to R): Pilot Mike Smith, Commander, Dick Scobee and Mission Specialist, Ron McNair.
Wayne Hale, a former space shuttle program manager and flight director who was working at NASA during both space shuttle accidents said:

"It just always gives us pause at this time of the year, those of us that are in the industry, to reflect on our sad experiences in the past and the lives of those that made such a great contribution to our country,"

It says from Fox News,
While an accident review board never conclusively determined what ignited the fire, a series of design flaws were blamed for making the module so flammable and difficult to quickly escape from. The investigation into the disaster delayed the Apollo program by more than a year-and-a-half and led to redesigns for the Apollo module, as well as procedural changes at NASA.

"We have not forgotten the lessons from Apollo, and I sure hope we as an agency don’t forget these lessons we have learned," said Bill Gerstenmaier, NASA's associate administrator for space operations.

Christa Mcauliffe was one of the crews who died from the accident. The space shuttle Challenger broke apart 73 seconds after lifting off on the orbiter's 10th flight on Jan. 28, 1986.