WASHINGTON (AP) — The head of the National Transportation Safety Board says investigators will be looking at every possible factor as they try to determine what caused a South Korean airliner to crash on landing in San Francisco yesterday.

The flight data recorder from Asiana Airlines flight 214 has been sent to Washington, D.C., for examination and investigators also plan to interview the pilots, crew and passengers.

NTSB chief Deborah Hersman says another element that will be considered is the shutdown of a navigational aid called a glide slope that helps pilots stay on course while landing. The ground-based aid had been shut down since June, but Hersman says pilots were sent a notice warning that it 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.