Look back: Flight 93 memorial under construction

Published: Aug 24 2011 09:58:27 AM EDT
Flight 93 Memorial 5

The memorial to United Flight 93, which crashed in a Pennsylvania field on Sept. 11 after passengers fought back against the men who hijacked their plane, is set to open on the 10th anniversary of the attacks. Take a look at some of the work that went into building the memorial.