The pilot, left in sole control of the aircraft after the captain left the cockpit, refused to open the door and pressed a button that sent the jet into its fatal descent.
The increase from the previous layout of 525 seats relies on a denser cabin configuration using 11 seats in each economy row instead of the current 10.
No international trade rules or precedent by the US exists for addressing airline subsidy claims, presenting a challenge for the administration, sources say.
The administration asked U.S. airline representatives about 20 questions in writing last week about their method in determining the subsidy allegations.