Published: Jul 07, 2013 12:30 PM EDT

 An aviation safety official says accident investigators are looking into what role the shutdown of a key navigational aid may have played in the San Francisco

plane crash.  National Transportation Safety Board Chairman Deborah Hersman says the glide slope - a ground-based aid that helps pilots stay on course

while landing - had been shut down since June.  She says pilots were sent a notice warning that the glide slope wasn't available.  Hersman tells CBS' "Face the

Nation" that there were many other navigation tools available to help pilots land. She says investigators will be "taking a look at it all." The Asiana Airlines

plane crashed as it was about to land Saturday, breaking off its tail and catching fire.

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