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PHILADELPHIA (AP)- Federal safety officials plan to question representatives from engine maker CFM International and Boeing about the fatal accident on a Southwest Airlines jet this year.

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Picture of window 14 with portion of engine inboard fan cowl.

The National Transportation Safety Board hearing Wednesday in Washington, D.C., is expected to last several hours.

The board is still investigating the April 17 accident, in which an engine fan blade broke and debris hit the plane, killing a woman who was blown partly out a broken window. Pilots landed the crippled plane safely in Philadelphia.

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Credit Marty Martinez

Investigators are focusing on the design and inspection of engine fan blades. After the accident, CFM recommended more advanced and frequent blade inspections, and regulators made those changes mandatory.

They will also look into the design of the engine housing, which is supposed to prevent pieces from breaking loose.

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