Getty images

Getty Images : "..Explosion rocks one of the World Trade Center Towers..."

Getty images http://www.gettyimages.com/ has a large collection of 9-11 related images .
You can not see the full-resolution images at the site (it's a shop) but still an excellent source
for researchers .
I found them by making a date-search for the period 9-11-2001 - 9-12-2001 . Interestingly, this also brings up images
from the USS George Washington, reported by USAToday to be anchored off Long Island on 9/11 http://home.att.net/~south.tower/911AirBase1.htm
Also see http://memes.org/russians-say-a3-navy-jet-struck-pentagon-launched-uss-george-washington

Below are some examples of images they have for sale :

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"World Trade Center Hit by Two Planes
394263 01: (PUERTO RICO OUT) An explosion rocks one of the World Trade Center Towers crumbled down after a plane hit the building. (Photo by Jose Jimenez/Primera Hora/Getty Images)

Image #: 1161244
License type: Rights-managed
Photographer: Jose Jimenez/Primera Hora/Stringer
Collection: Getty Images News
Source: Getty Images North America
Credit: Getty Images