The "missing man" formation concluded the memorial services at JSC for the STS 51-L crew. Four NASA T-38 jet aircraft were used for the symbolic flight. A small portion of the crowd is visible in the bottom portion of the frame.
From Nick Greene, former About.com Guide
Space Shuttle Challenger Disaster STS-51L Pictures - The "missing man" formation concluded the memorial for the STS 51-L crewNASA Johnson Space Center (NASA-JSC)